Thanks for outlining how you understand the word. — Ludwig V

You're welcome. FWIW, I was going for an understanding of "common-sense reality," not "reality" as such, which is very hard to use effectively at all.

I'm fascinated by the temptation (which I partly share) to deny that tables and rocks are "really" solid when the explanation actually affirms, and does not deny, that solidity is, in everyday contexts, exactly what it seems to be. The same phenomenon is capable of two different and incompatible interpretations. What can we make of this? — Ludwig V

I think we can dissolve the problem by pointing to the equivocations. "Solid" can mean a couple of different things, and it's only when the uses get confused that it looks like there's a problem. I'm not sure they're even incompatible, at least not in a puzzling sense -- as you say, we get a deeper, more accurate explanation for how good old common-sense "solidity" is actually accomplished.

I agree that bringing in "really" as a qualifier for "solid" is hopeless!

Part of that is noticing that Cartesian scepticism is not the only variety of scepticism, — Ludwig V

I'm reading Bernard Williams' book on Descartes at the moment, and he reminds us that Descartes several times warns us not to take his methodical doubt as genuine doubt -- the sort of doubt it might be reasonable to have about, say, sense perceptions. In the Discourse, he contrasts his method with what we normally do, which is to "follow opinions which one knows to be very uncertain, just as though they were indubitable." Instead, for the purposes of his project:

I thought it was necessary that I do just the opposite, and that I should reject, just as though it were absolutely false, everything in which I could imagine the slightest doubt. . . So, since our senses deceive us sometimes [my emphasis] I wished to suppose that there was nothing which was as they make us imagine. — Discourse on the Method, VI 31-32

As Williams discusses, Descartes is not trying to say that it is in any way reasonable to go from "can deceive us sometimes" to "deserve to be doubted as a whole." This is a philosophical method designed to find some criteria for knowledge, not a way of life. Why such a methodical, unreasonable doubt would help us do this, is another story, which Descartes goes on to explain.

The deeper question that I think we should be talking about is what lies behind the ancient philosophical tradition of denying common sense reality. — Ludwig V

I've said why. Often, 'common sense' is absolute horseshit. That's why we have things like 'folk psychology' to dismiss. Obviously, that's not the end of the story is there is something weighty to what Banno is saying, but it doesn't butter bread for the fact that quite often (and far more often, with lay people (what that says, I don't care in the present moment)) the world turns out to not be as it is. Given that this is the case, 'common sense' isn't quite 'common' as it seems. I think all 'common sense' says is that there are ways of thinking that tend toward problem solving in real time. Lots of people are not able to do this.

The explanation for solidity is not the somewhat vague idea probably everyone has before learning what's really going on. — Patterner

Here's a funny thing: After learning that atoms are mostly space, one does not find oneself sinking into one's arm chair. Things remain solid.

Learning that atoms are mostly space does not change the fact that arm chairs are solid. Both are true.

If there is a problem of perception here, it is the misperception that things consisting mostly of space cannot also be solid.

Long ago, when I was philosophically active, there was a widespread opinion that scepticism was vanquished and could be put to bed (or its grave). It turns out that was not so. It seems to be still alive and kicking. — Ludwig V

I suspect this is only so amongst apprentices, and the occasional journeyman. I'll maintain that Austin and Wittgenstein put the sort of scepticism in the quite well written OP to bed.

Long ago, when I was philosophically active, there was a widespread opinion that scepticism was vanquished and could be put to bed (or its grave). It turns out that was not so. It seems to be still alive and kicking. Cavell was right - we need to get deeper into the phenomenon and understand better where it comes from. Part of that is noticing that Cartesian scepticism is not the only variety of scepticism, and that denial of common sense reality goes back a long way in philosophy, arguably right back to the beginning. It may be that it is an essential feature of any enquiry that we might recognize as philosophical. But it also seems to be found useful in religion - another point where religion and philosophy seem to coincide or at least to be near neighbours.

It's a very interesting question why radical skepticism existed in the ancient world (and was indeed somewhat popular for the sort of position it is, being addressed across centuries from Parmenides to Augustine) but not really anything quite like Cartesian skepticism.

I think part of the problem of attempts to "put skepticism to bed," is that they are often using something like Kripke's "skeptical solutions." For instance, in his context, "the argument from underdetermination has real strength and cannot be defeated... but that's ok because..." There is something similar going on in Quine, and a lot of other thinkers. So, perhaps it's partly that the skeptical solutions are not considered acceptable, or are themselves considered to be radically skeptical. I have certainly seen philosophers say this, not only about Wittgenstein, etc., but even about Kant's attempted solution. And then Hume was self consciously riffing on ancient skepticism.

There was, however, a pretty long period between the decline of the Academics and Descartes where skepticism was, if not entirely dead, at least in a coma, which is interesting too.

One interesting historical facet is that the original Empiricists (Sextus and co.) were seen as skeptics, and for reasons not that unlike Hume, and the later modern traditions type of arguments (underdetermination being the common thread I can see, but also, while not a common metaphysics, a denial of common metaphysical positions).

IDK, I'd love to find a good treatment of the history. My inclination is that some of the resistance might also have to do with the "thin" anthropology used in some resolutions to skepticism, which is unappealing to some.

The deeper question that I think we should be talking about is what lies behind the ancient philosophical tradition of denying common sense reality. — Ludwig V

What lies behind the traditional philosophical denial of common sense would seem to be the assumption that this world, not being perfect, cannot be the true world. The human desire for a transcendent reality, as opposed to this "mere shadow world" has a lot to do with the desire for life to be fair―that is to punish the wicked hereafter when they elude punishment down here, and to provide us with salvation and eternal life. Most of us would rather not die; so being in denial of the fact of death is one strongly motivated strategy for coping with it.

I've said why. Often, 'common sense' is absolute horseshit. That's why we have things like 'folk psychology' to dismiss. — AmadeusD

Some common sense may be based on illusion to be sure. The idea we have of the nature of consciousness and self are good candidates. On the other hand if such "folk" notions cannot be definitively refuted, and if they are "native" to the human mind, then perhaps they serve a useful purpose, even though they tell us nothing substantive about the real nature of things―given that the real nature of things in the ultimate sense that the human mind seems so addicted to entertaining is not at all decidable.

Yes, that could also be true. There's some argument around fear of snakes, for instance, despite the risk of snake attacks being low. That may be something in-built, as it were and not at all telling us anything about hte world.

given that the real nature of things in the ultimate sense that the human mind seems so addicted to entertaining, is not at all decidable. — Janus

(I added a comma for ease of reading). I agree.

I'm reading Bernard Williams' book on Descartes at the moment, — J

I've very tempted to engage with this, but I'll have to save that treat for another time. For now, let me just say that even if Cartesian scepticism has been resolved, I'm sure that people will continue to read and discuss Descartes' account, just as people still read Plato and Berkeley.

Descartes several times warns us not to take his methodical doubt as genuine doubt -- the sort of doubt it might be reasonable to have about, say, sense perceptions. — J

I'm sure it's an excellent book and people do seem to forget that quite often. But do we really understand what methodical doubt means, if it does not mean doubt? The only thing that is clear is that the normal context in which we understand what doubt is, is set aside. So what does this amount to?

Often, 'common sense' is absolute horseshit. That's why we have things like 'folk psychology' to dismiss. — AmadeusD

I would be the last person to deny that. There's a lot of it about. But it's as well to be selective in what one dismisses out of hand.

There's some argument around fear of snakes, for instance, despite the risk of snake attacks being low. That may be something in-built, as it were and not at all telling us anything about hte world. — AmadeusD

That may well be true. I put it down to the "otherness" of snakes - and spiders, especially big ones - and we are programmed to be suspicious of other, incomprehensible, creatures.

If there is a problem of perception here, it is the misperception that things consisting mostly of space cannot also be solid. — Banno

Well, I do think that, in the absence of countervailing evidence it seems natural to regard solid things as those that occupy space, just as it seems natural to suppose that the earth is flat, and static - and to wonder what it rests on.

I suspect this is only so amongst apprentices, and the occasional journeyman. — Banno

Maybe you are right. But I don't find it easy to work out in this very special environment who is apprentice and who is professor - and, as Cicero pointed out, there is nothing so absurd that some philosopher will not believe it. (I will refrain from citing examples.)

So, perhaps it's partly that the skeptical solutions are not considered acceptable, or are themselves considered to be radically skeptical. I have certainly seen philosophers say this, not only about Wittgenstein, etc., but even about Kant's attempted solution. And then Hume was self consciously riffing on ancient skepticism. — Count Timothy von Icarus

You put your finger on a fascinating phenomenon. When I returned to Hume recently, I was astonished to find that he is not at all what I would consider a sceptical philosopher; then I realized that Descartes' reputation is also a complete misunderstanding, since his project was precisely to resolve the nightmare he conjures up. The same goes for others, as well. It's very confusing. Is there any philosopher since Descartes who has actually defended, as opposed to trying to resolve, scepticism? Earlier scepticism was different in that it was proposed as a basis for achieving ataraxia or apatheia and so living a happy life.

IDK, I'd love to find a good treatment of the history. My inclination is that some of the resistance might also have to do with the "thin" anthropology used in some resolutions to skepticism, which is unappealing to some. — Count Timothy von Icarus

I'm afraid I can't help you. By "thin" anthropology, do you mean the sketchy references to ways of life and/or evolution? It's difficult being a philosopher and wanting to take allied discussion in other departments seriously. There just isn't time. Or that's my excuse.

What lies behind the traditional philosophical denial of common sense would seem to be the assumption that this world, not being perfect, cannot be the true world. The human desire for a transcendent reality, as opposed to this "mere shadow world" has a lot to do with the desire for life to be fair―that is to punish the wicked hereafter when they elude punishment down here, and to provide us with salvation and eternal life. Most of us would rather not die; so being in denial of the fact of death is one strongly motivated strategy for coping with it. — Janus

Yes, all of that. Ethics in general, and justice in particular, is an interesting combination of incompatible desires. On the one hand, the desire of the powerless to restrain the powerful and on the other hand, the desire of the powerful to control the powerless.

given that the real nature of things in the ultimate sense that the human mind seems so addicted to entertaining is not at all decidable. — Janus

Perhaps the ability and desire to push things further is what lies behind the tendency to look for ever more ultimate ultimates and get lost, as it were, in outer space. That's one thing that I don't see in non-human animals.

The deeper question that I think we should be talking about is what lies behind the ancient philosophical tradition of denying common sense reality. — Ludwig V

Two cents:

Given that common sense reality just means we know things as they are, my understanding of the tradition of denying common sense reality, stems from the major premise contained in at least some versions of that tradition, that the human cognitive system is representational, in that everything to which it is directed is mere affected senses, re: sensation, from which alone no cognition is at all possible.

However deep the question, whether it should be talked about or not is governed by who’s talking. To those who insist a chair is a chair, tend to neglect how it came to be one….probably less than profitable.

But do we really understand what methodical doubt means, if it does not mean doubt? — Ludwig V

Is there any philosopher since Descartes who has actually defended, as opposed to trying to resolve, scepticism? — Ludwig V

I'll respect your wish not to engage with Descartes at the moment, though I'd enjoy that conversation. Suffice it to say, both your questions deserve thoughtful answers.

Here's a funny thing: After learning that atoms are mostly space, one does not find oneself sinking into one's arm chair. Things remain solid. — Banno

Go figure.

I will, however, point out that the reason the X-Men's Kate Pryde can pass through solid objects is because she's able to take advantage of the spaces between. So there's that.

I think Dave Matthews Band's The Space Between is a great song.

You put your finger on a fascinating phenomenon. When I returned to Hume recently, I was astonished to find that he is not at all what I would consider a sceptical philosopher; then I realized that Descartes' reputation is also a complete misunderstanding, since his project was precisely to resolve the nightmare he conjures up. The same goes for others, as well. It's very confusing. Is there any philosopher since Descartes who has actually defended, as opposed to trying to resolve, scepticism? Earlier scepticism was different in that it was proposed as a basis for achieving ataraxia or apatheia and so living a happy life.

Yes, you raise a good point. By "skeptical" I think many critics of "skepticism" do mean precisely a methodological skepticism. This move essentially tears up most of the "web of belief," including central threads, and then attempts to rebuild the entire thing based on a very small set of remaining presuppositions. As I mentioned in an earlier thread, I think this has the effect of making philosophy chaotic, as in "strongly susceptible to initial conditions," where you get radically different "skeptical solutions," based on which part of the web was allowed to remain standing at the outset. Hence, a very large diversity of "camps" or "schools" developing out of common sorts of skepticism as a methodological starting point. Also, appeals to pragmatism over truth here seem to make the difference between the camps seem less secure.

This is different from an approach that starts from what is known and then tries to explain a metaphysics of knowledge. In terms of empiricism, this wasn't unknown to the ancients. Gerson has a good article on Neoplatonic epistemology, and this was basically Plotinus' camp's main thrust, that the empiricist is incapable of knowing anything. They only know something like representations of things, and can never step outside them to compare them with reality, and underdetermination leads them towards equipollence, which might aid ataraxia, but certainly not any further move into the erotic ascent and henosis. But if an epistemology cannot secure even our most basic, bedrock beliefs, what we already "know we know," then the claim is that the epistemology has obviously failed.

Plus, the modern paranoid or depressed skeptic is basically following the same route and just taking different emotional import from this.

In this context, I can absolutely see why Hume is considered a skeptic. His position is skeptical re causes as generally understood. Saying "x can't exist or be attained so we should use the word x for y instead," (e.g. constant conjunction for causes, deflation, something limited to a specific human game, or coherence for truth, objective for the phenomenal realm, etc.) is arguably an equivocation and denial of the original x, or at least that's the critics' claim (and the claim of some supporters who embrace skepticism as the proper conclusion of these arguments.) This is not unlike how the immediate successors of Kant took his philosophy into dualism and subjective idealism, even though his letters show he didn't want to reach these conclusions. But what one wants and what one's philosophy suggests or at least allows (fails to exclude), can two different things.

There is also Hume's thing about consigning the bulk of non-empirical human "knowledge" and past philosophy to the flames, or the unresolved problem of induction (made particularly acute by the prior move to make abstraction a sort of induction) being resolved by just playing billiards and forgetting about it. So too, the guillotine sort of assumes at least a mild sort of anti-realism as a premise, since if anything can be "truly good" if can presumably be "truly choiceworthy," and thus there can be syllogisms using facts about the choiceworthyness of actions that suggest (although do not force) action.

Is there any philosopher since Descartes who has actually defended, as opposed to trying to resolve, scepticism? — Ludwig V

If it be allowed that scepticism as such, is, “….the principle of a technical and scientific ignorance, which undermines the foundations of all knowledge, in order, if possible, to destroy our belief and confidence therein….”, Kant treats scepticism as a natural prerogative or intrinsic condition of reason itself, its ubiquitous nature thereby mandating it best be done properly, which just means to be sceptical in accordance with a method by which one is“….endeavouring to discover in a conflict of this kind, conducted honestly and intelligently on both sides, the point of misunderstanding…”.

So it can be said scepticism, at least in this form, is both defended insofar as it is inescapable, and, resolved insofar as it is subjected to a proper method.

human cognitive system is representational, in that everything to which it is directed is mere affected senses, re: sensation, from which alone no cognition is at all possible. — Mww

I'm not sure I understand all of this. But I do agree that representing our "cognitive system" as representational does indeed set one up for scepticism about the things that are supposed to be represented. Just one more reason not to set oneself up in that way in the first place.

I'll respect your wish not to engage with Descartes at the moment, though I'd enjoy that conversation. Suffice it to say, both your questions deserve thoughtful answers. — J

I can resist anything except temptation. I would welcome reading your answers.

This is different from an approach that starts from what is known and then tries to explain a metaphysics of knowledge. — Count Timothy von Icarus

That sounds like Aristotle, and I must admit, it makes more sense to me. One must remember, however, that he is also quite content to revise the knowledge that is handed down to him when necessary
; it is not sacrosanct or immune from doubt or anything like that. In specific circumstances, questioning one's presuppositions, beginning again with a clean slate are perfectly reasonable tactics. But as an approach to all knowledge, from the beginning,.... that's a different matter.

There is also Hume's thing about consigning the bulk of human "knowledge" and past philosophy to the flames, or the unresolved problem of induction (made particularly acute by the prior move to make abstraction a sort of induction) being resolved by just playing billiards and forgetting about it. — Count Timothy von Icarus

If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. — David Hume - An Enquiry Concerning Human Understanding sec. 12, pt. 3

I don't think you are being fair to him.
1. It's not the really the bulk of human knowledge that's in danger - just "divinity and metaphysics".
2. His view of abstraction is somewhat similar to his idea of induction, but lacks the problematic element of making predictions.
3. You may not like his resolution of the induction issue, but he does at least provide a candidate. Admittedly, it involves accepting that empirical observations cannot justify a generalization, but then explaining that we humans are just going to continue to rely on it, justified or not. What's wrong with that?
4. Hume's key complaint about radical, Pyrrhonic scepticism is that it makes no difference to anything. So even though it may be sound, it is of no consequence. It is for that reason that he recommends ignoring it.

So it can be said scepticism, at least in this form, is both defended insofar as it is inescapable, and, resolved insofar as it is subjected to a proper method. — Mww

I suppose so. But then, the same could be said of both Descartes and Hume who are usually considered sceptical philosophers.

That sounds like Aristotle, and I must admit, it makes more sense to me. One must remember, however, that he is also quite content to revise the knowledge that is handed down to him when necessary
; it is not sacrosanct or immune from doubt or anything like that. In specific circumstances, questioning one's presuppositions, beginning again with a clean slate are perfectly reasonable tactics. But as an approach to all knowledge, from the beginning,.... that's a different matter.

Yes, and many others. And yes, certainly things can be revised, even radically so. That's why I'd say the difference is methodological. Post-Descatres, there is an extreme focus on method, while philosophy also starts to be thought of more as a "system" or "game." So, even though many later thinkers in this mold are adamantly "anti-foundationalist," they still retain this orientation towards foundational skepticism and the idea that method can overcome it and "build back."

I don't think you are being fair to him.

Yeah that's fair, it wasn't clear as written; "human" should be "humanist." That is, "the bulk of non-empirical human knowledge," as in (but not exclusively) "the humanities," due to his epistemic standards. E.g., "morals and criticism are not so properly objects of the understanding as of taste and sentiment. Beauty, whether moral or natural, is felt, more properly than perceived," when combined with the prior claims about history, etc. being grounded in observations of particulars, would seem to exclude most of the classical education's curriculum ("humanist knowledge," not "human knowledge"). Writers in the "Canon" like Plutarch, Tacitus, Juvenal, Cicero, etc. would be mostly valuable for the observations of fact they record under such criteria (probably the least useful thing about them), and this would seem to hit folks like Confucius too.

Obviously, he doesn't really seem to intend that we should burn these (at least I don't think so), but rather that they don't represent knowledge.

Arguably, I think we could also take the precepts as sort of demoting the authority of techne, i.e. arts, and indeed there is an interesting relationship between moral anti-realism, which affects our understanding of ends, and the arts, which are defined by ends, but seem to also involve "the understanding" and expertise. I'd have to reread it again though. Certainly, I think this demotion occurs at some point before the 20th century though (the speculative sciences were always ranked higher in a way, but not to the same extent). For instance, if you try to justify moral realism by appealing to the "facts" known by medical science, you will often face the objection that medicine is not really a science precisely because it is a productive art, whereas medicine as the "science" the the healthy body is all over older philosophy, even though it is also recognized as an art.

1. It's not the really the bulk of human knowledge that's in danger - just "divinity and metaphysics".

I think the preceding sections suggest that it's everything that isn't occurring according to observation or the relatively narrow range of the a priori; those topics are just particularly bad offenders. We're not really burning them, but we're downgrading them to taste and sentiment.

But, I am sympathetic to thinkers who say that moral ant-realism or skepticism is itself a sort of radical skepticism (i.e. not limiting it to theoretical knowledge). For one, if nothing is ever truly good, then truth cannot be truly better than falsity, "good faith" good, and so too for "good methods," or "good argument," since these all relate to ends, i.e. "the Good," "that at which all things aim."

2. His view of abstraction is somewhat similar to his idea of induction, but lacks the problematic element of making predictions.

Right, and this view of abstraction is what aids the deflation of causation. This isn't really Hume's idea though, it's in earlier thinkers and goes back to Ockham in its etiology; Hume is just following the dominant trend in Anglo philosophy to its logical conclusion. He is a brilliant diagnostician in this sense.

3. You may not like his resolution of the induction issue, but he does at least provide a candidate. Admittedly, it involves accepting that empirical observations cannot justify a generalization, but then explaining that we humans are just going to continue to rely on it, justified or not. What's wrong with that?

It's still a "skeptical solution," though right? That was my point, people don't find these compelling (particularly the appeals to pragmatism, because arguably the skepticism also affects our knowledge of whether anything is ever truly useful). So, even if I did like his solution, I could still see why some people aren't satisfied with it and embrace a more "depressed/anxious" skepticism instead. That is, they simply do decide to worry about it, and I cannot really blame them for that. For instance, for Bertrand Russel, Hume's case implied that "there is no intellectual difference between sanity and insanity."

I can resist anything except temptation. I would welcome reading your answers. — Ludwig V

Very good, Oscar. :wink:

But do we really understand what methodical doubt means, if it does not mean doubt? — Ludwig V

It does mean doubt, but applied in a special way. I think Cartesian methodical doubt has two negative characteristics:

It is not a means of questioning each experience we may have, to determine if it is "real."

It is not supposed to carry over into daily life at all, but rather serve as a method for discovering what we may know for certain.

To the first point, Bernard Williams puts it succinctly: "There is the universal possibility of illusion, and there is the possibility of universal illusion." Descartes argues that any given perceptual experience might be illusory (based on the idea that we may be dreaming). But this does not mean that perceptual experience in toto must be unreliable. These are two different thoughts; the latter does not follow from the former. You can believe that any given X is illusory without also having to believe that, therefore, all Xs are illusory.

So this is not an attempt to determine what must in fact be illusory. It is not a method we take into our everyday experiences. Neither the specific nor the general sort of doubt is being asserted. At this juncture, Descartes wants to know what is possible, not what is true. His idea is that, if we can find something about which not even the possibility of doubt can be raised, we will have found a foundation upon which to build our knowledge of the world.

Does that fit your sense of Descartes' project?

Is there any philosopher since Descartes who has actually defended, as opposed to trying to resolve, scepticism? — Ludwig V

So if the above sketch is on the mark, then I'd say that Descartes does not defend skepticism at all. Really, he wants to defeat it. His methodical doubt is a version of giving the Devil his due, of being willing to concede every conceivable lack of certainty in the interests of making his case strong. Had Descartes used this method and discovered nothing that was certain (and been able to rest content with that), I'd call him a skeptic, if an unhappy one.

I've never been quite sure why Descartes is sometimes seen as "introducing doubt" or "questioning certainty" of previously unshakable ideas. He is merely pointing out, correctly, that the possibility of doubt exists in the places he names. At no point does he recommend that we in fact doubt sense perceptions, either one by one or collectively. In a letter to one of his critics, he says:

A man decides to eat nothing, because he’s never certain that his food hasn’t been poisoned, and he thinks that he isn’t obliged to eat when it isn’t transparently clear that the food will keep him alive, and that it is better to wait for death by abstaining than to kill himself by eating. Such a man would be rightly regarded as mad and as responsible for his own death. — Descartes to Hyperaspistes, viii.1641

Descartes compares this to an absurd practical attitude of constant "methodical doubt" and concludes: "This is so self-evident to everyone that I’m surprised that anyone could think otherwise."

What lies behind the traditional philosophical denial of common sense would seem to be the assumption that this world, not being perfect, cannot be the true world. The human desire for a transcendent reality, as opposed to this "mere shadow world" [ ... ] — Janus

:fire:

I think Dave Matthews Band's The Space Between is a great song. — Patterner

Yessir.

On the one hand, the desire of the powerless to restrain the powerful and on the other hand, the desire of the powerful to control the powerless. — Ludwig V

The inability of the powerless to coordinate in order to restrain the powerful just might be a candidate for the major source of human misery―the central pathos of the human condition.

Perhaps the ability and desire to push things further is what lies behind the tendency to look for ever more ultimate ultimates and get lost, as it were, in outer space. That's one thing that I don't see in non-human animals. — Ludwig V

Right, that certainly seems to be a major human tendency. I also think humans love to pull things apart to see how they work, and then that search for constitutive function focuses on the smaller and smaller and smaller.. Both of these searches―for the greatest overarching principles and the smallest constitutive entities would seem to be impossible without symbolic language, which is probably why we don't see such concerns in other animals―and there would also seem to be a powerful element of misleading reification in both.

"human" should be "humanist." That is, "the bulk of non-empirical human knowledge," as in (but not exclusively) "the humanities," — Count Timothy von Icarus

He may well have had that target in his sights.

We're not really burning them, but we're downgrading them to taste and sentiment. — Count Timothy von Icarus

H'm. That is certainly what was happening, though paradoxically during the next century or so, the humanities also got elevated to the sure sign of being a civilized person - and essential for the gentry who did not need to earn their own living.

But, I am sympathetic to thinkers who say that moral ant-realism or skepticism is itself a sort of radical skepticism (i.e. not limiting it to theoretical knowledge). For one, if nothing is ever truly good, then truth cannot be truly better than falsity, "good faith" good, and so too for "good methods," or "good argument," since these all relate to ends, i.e. "the Good," "that at which all things aim." — Count Timothy von Icarus

Well, from the point of view of a realist, that would indeed seem to be so. But if you don't have and/or can't recognize, the Good, but, perhaps, only a range of activities and/or ends that are worthwhile in their own right, then moral anti-realism seems less like a form of scepticism. To be clear, for someone who doesn't but Aristotle's crowning of the hierarchy of purposes, or who thinks that the supposed crown is an illusion, "truly good" is just rhetorical pleonasm.

Post-Descatres, there is an extreme focus on method, while philosophy also starts to be thought of more as a "system" or "game." — Count Timothy von Icarus

Yes. Philosophers are very good at buying in to the latest intellectual developments, and, mostly, making too much of them. They usually settle down after 100 years or so.

For instance, for Bertrand Russel, Hume's case implied that "there is no intellectual difference between sanity and insanity." — Count Timothy von Icarus

Accusations of insanity are quite near the surface of philosophical argument. After all, not so long ago and during Russell's lifetime, a philosophical thesis was either true and trivial or nonsense. It was a high-stakes game. Fortunately, psychiatrists didn't buy into that mistake - they were busy making different mistakes.

The inability of the powerless to coordinate in order to restrain the powerful just might be a candidate for the major source of human misery―the central pathos of the human condition. — Janus

Yes, indeed. Though, of course, the powerful, when they are not complacent, live in fear that the powerless will get themselves together - and then they are unstoppable. Cardinal Bellamine said it best - "The voice of the people is the voice of God".

I also think humans love to pull things apart to see how they work, and then that search for constitutive function focuses on the smaller and smaller and smaller.. Both of these searches―for the greatest overarching principles and the smallest constitutive entities would seem to be impossible without symbolic language, which is probably why we don't see such concerns in other animals―and there would also seem to be a powerful element of misleading reification in both. — Janus

Yes, symbolic language is very important. But I get worried when people try to deduce that we are not animals.
Reification is a major curse for any philosopher that has an ear (eye) for language.

A preface. David Hume draws a sharp distinction, between what he calls Pyrrhonistic or radical scepticism and what he calls judicious scepticism. It is the former that he disapproves of. But he also thinks that judicious scepticism, which is cautious balanced judgement, is an important virtue in life. I think that's right. He doesn't mention Descartes, which is annoying, but I think that Descartes would count as a Pyrrhonistic sceptic.

Does that fit your sense of Descartes' project? — J

It fits my sense of his project. But I don't like the project.

To the first point, Bernard Williams puts it succinctly: "There is the universal possibility of illusion, and there is the possibility of universal illusion." — J

Yes, that's right. So there are two versions of what is going on. I think you will find that the distinction is often not drawn, but I may be wrong. In any case, if you (and perhaps WIlliams) grant that the project of doubting everything is incoherent, we are left with the examination of specific doubts.

The programme is to consider each of our doubts, in order to distinguish the uncertain from the certain. He needs, therefore, to exempt from scrutiny all the knowledge that enables him to distinguish between truth and falsity.
In fact, he exempts a number of other things from his examination. One of them is his own sanity - he does not think that he is an emperor. Another is that his senses do not always deceive him, though he seems to forget that in other passages.
If I asked you to believe that I am going to spend my week-end on the moon, could you do it? Or would you look for some evidence and fit your belief to the evidence? Doubting without evidence is not rational, and sticking "methodical" in front of the doubt does not make any difference to that. You could easily pretend to believe me, but somehow I don't think that's what Descartes had in mind.

He wants us to set aside our practical, moral and aesthetic concerns and think about the apple in a completely disinterested way. He does not consider that to think about the apple in that way (a theoretical stance) may be to be unable to think about the apple as we know it.

So this is not an attempt to determine what must in fact be illusory. It is not a method we take into our everyday experiences. Neither the specific nor the general sort of doubt is being asserted. At this juncture, Descartes wants to know what is possible, not what is true. His idea is that, if we can find something about which not even the possibility of doubt can be raised, we will have found a foundation upon which to build our knowledge of the world. — J

That is in interesting change. But I don't think it changes much,
In any case, the question of what is possible is not at all clear. Many people believe that it is possible that the sun will not rise tomorrow morning, simply because it is not self-contradictory to assert that it has not risen. Is it possible that I don't in fact have two hands? To put it another way, someone who thinks that it is possible that he is being duped by an evil demon has a pretty elastic sense of what is possible.
The model of mathematical knowledge, particular geometry on the moden of Euclid, is in the background here. Because of Euclid's approach, it seems that a meaning can be given to the idea of foundations of knowledge. Whatever we may say about that approach in mathematics, it does not follow that the same model will work for all knowledge, particularly if the proposal is for one system for all knowledge.
What do you mean by saying that he is not asserting his doubt? Are all his assertions in Meditation 1 not really assertions? They certainly conform to the normal requirements for asserting doubt.

So if the above sketch is on the mark, then I'd say that Descartes does not defend skepticism at all. Really, he wants to defeat it. — J

Yes, I'll give him that. The trouble is that he has discovered a methodology that runs out of control and doubts too much.

Descartes compares this to an absurd practical attitude of constant "methodical doubt" and concludes: "This is so self-evident to everyone that I’m surprised that anyone could think otherwise." — J

But all he does here is to announce that we are not supposed to take our methodical doubts seriously. Which undermines the entire project. He wants to prevent that, but all he can say is "But I never meant it that way". We need a bit more than that, don't you think?

Yes, I'm being difficult. Some readers might feel that I should be more charitable. I'm not sure about that. I don't doubt his sincerity, by the way, though some people do argue that he is insincere.

Well, from the point of view of a realist, that would indeed seem to be so. But if you don't have and/or can't recognize, the Good, but, perhaps, only a range of activities and/or ends that are worthwhile in their own right, then moral anti-realism seems less like a form of scepticism. To be clear, for someone who doesn't but Aristotle's crowning of the hierarchy of purposes, or who thinks that the supposed crown is an illusion, "truly good" is just rhetorical pleonasm.

Aristotle's Ethics is focused on just this question though, identifying what is sought for its own sake. Wouldn't the anti-realist position rather be that nothing is truly more or less desirable, that "desirable" just means "whatever we just so happen to currently desire." So, whenever falsity is preferred to truth, bad faith perceived as more "useful" than good faith, etc., it is simply better, because "better" just means "I prefer." That's the popular summary statement of emotivism: "x is good" just means "hoorah for x," and "y is bad," just means "boohoo for y." As Hamlet says, "nothing is either good or bad but thinking makes it so."

Of course, few anti-realists deny that things can be better or worse vis-a-vis some ends, since this seems absurd. So normally it is the claim that ends themselves cannot be judged better or worse, normally packaged with a denial of the rational appetites (the desire for truth and goodness themselves) so that even rather obvious ends like "not being lit on fire" must stem from a sort of arational sentiment/feeling (this being the result of the axiomatic the denial of rational appetites). Anti-realism is also made more plausible by the Enlightenment division of the good, such that the good of the appetites is divorced from a sui generis "moral good," so that one doesn't have to deny things like: "it is bad for men to be lit on fire," but only the amorphous declaration that "lighting men on fire is 'morally' bad."

Hence, "truly better or worse" can still be used by some anti-realists. Different race cars can be truly better or worse; some are faster. You can have truly better or worse choices for which school you attend, which vacation you go on, etc.. It's rather the "moral good" that is denied. But the counter is that this "moral good" is incoherent, and that the topics of ethics is so bound up in practical reason as a whole that the denial of this new category doesn't actually secure anti-realism the way the anti-realist thinks it does, or at the very least is an inappropriate category for analyzing pre-Enlightenment ethics (Western and Eastern).

A preface. David Hume draws a sharp distinction, between what he calls Pyrrhonistic or radical scepticism and what he calls judicious scepticism. It is the former that he disapproves of. But he also thinks that judicious scepticism, which is cautious balanced judgement, is an important virtue in life. I think that's right. He doesn't mention Descartes, which is annoying, but I think that Descartes would count as a Pyrrhonistic sceptic.

Right, although the common criticism is that this isn't actually justified, making it an arbitrary sentiment tacked on to what appears to be good grounds for skepticism (if we accept the argument). Not wanting to endorse a position and arguing for positions that imply that self-same position are two different things, and thinkers often do both. That, and that he contradicts himself in trying to have his cake and eat it too, like when he argues from an is to an ought re treating children well a few pages after arguing for the impossibility of such a move.

Yes, I'm being difficult. Some readers might feel that I should be more charitable. — Ludwig V

Not at all. This moment in Western philosophy deserves the most careful scrutiny. And your reading is not uncharitable in the sense that you're determined to put the worst construction on what Descartes is saying. You, and I, both want simply to understand what he was up to.

I think we should take Descartes at his word when he says that he does not intend "methodical doubt" to be applied in daily life. His quoted words in the letter make that pretty clear, and Williams cites a number of other instances.

So we have to ask, Why, then, apply it as part of his Method? What can be achieved by conjuring up a sort of doubt that would never occur to us in real life? You say:

all he does here is to announce that we are not supposed to take our methodical doubts seriously. Which undermines the entire project. — Ludwig V

but I think he does more than that. He wants us to take methodical doubt very seriously indeed, as a method of ascertaining what might constitute certain knowledge. I called this a kind of "giving the Devil his due" skepticism; Williams calls it "pre-emptive skepticism," meaning much the same thing. Descartes wants certainty, not merely what seems overwhelmingly likely. So he's willing to make enormous concessions to what a hardened skeptic might claim.

Now here you may part company with his inventory of what could be doubted. You say:

Is it possible that I don't in fact have two hands? To put it another way, someone who thinks that it is possible that he is being duped by an evil demon has a pretty elastic sense of what is possible. — Ludwig V

Elastic is hardly the word! Descartes has to conceive the possibility that all his experiences (save one, as we will see) could be illusory. But -- his grounds for thinking that being two-handed could be doubted have nothing to do with comparing the certainty of this belief with the certainty of some other belief. Here, as with the demon, it is "the possibility of universal illusion." So if you want to say that Descartes goes too far here -- that there's no need for the rigamarole of methodical doubt because we already know what can't be doubted -- you'd have to show why the demon (or Matrix!) hypothesis is impossible. And there are a number of modern arguments, broadly analytic or Wittgensteinian in nature, that make that case.

I think generally when we affirm what is obvious, we do so by comparing the obvious thing with something less obvious, but that strategy is not open to you here, if you meet Descartes on his own ground. It's not that "I have two hands" must be shown to be indubitable, but rather that "whatever I affirm that I perceive clearly and distinctly" is indubitable -- that is, cannot, under any circumstances, be mistaken. So, with respect, this isn't quite it:

The programme is to consider each of our doubts, in order to distinguish the uncertain from the certain. — Ludwig V

That's just what Descartes finds self-evidently absurd. We're pushing doubt a level up, instead, and asking what is possible to doubt, not how we would go about settling an actual occasion of doubt.
And yes, I do indeed believe that Descartes is not asserting anything as in fact doubtful. Rather, he is asserting what may possibly be doubted. You say:

What do you mean by saying that he is not asserting his doubt? Are all his assertions in Meditation 1 not really assertions? They certainly conform to the normal requirements for asserting doubt. — Ludwig V

I don't think so. I read him as asserting what is possible, not what is the case. It's the difference between saying, "That bird could be an oriole" and "That bird is an oriole." These are both assertions; if I make the first one, it will be true if the bird could be an oriole, and false if it could not be. The second assertion says something quite different; it will be true if the bird is in fact an oriole, false if it is not. I believe the former mode is what Descartes is talking about.

Lots more to say on this subject! -- especially, we can go into a lot more depth about why Descartes has such faith in Methodical Doubt as a method that will lead to certainty. But I'll stop bending your ear -- tell me what you think.

Yes, indeed. Though, of course, the powerful, when they are not complacent, live in fear that the powerless will get themselves together - and then they are unstoppable. Cardinal Bellamine said it best - "The voice of the people is the voice of God". — Ludwig V

True, if the individually powerless could manage to coordinate and agree to act to secure their interests, the powerful would have no chance. It's just that, in the absence of egregious oppression and lack of quality of life, this never seems to happen.

Yes, symbolic language is very important. But I get worried when people try to deduce that we are not animals.
Reification is a major curse for any philosopher that has an ear (eye) for language. — Ludwig V

I think you know from past discussions that I would be the last to indulge in human exceptionalism and conclude that we are somehow more than mere animals. We are only exceptional inasmuch as we are very unusual animals. That said, there are also many other very unusual animals.

We're pushing doubt a level up, instead, and asking what is possible to doubt, not how we would go about settling an actual occasion of doubt. — J

It seems to me to be a question of what we can logically doubt, and I think the answer is 'anything that can be imagined to be false without logical contradiction'. It seems we cannot doubt the LNC itself without falling into incoherence.

The obverse is what we can absolutely certain of; and I think that would be only what is true by definition or according to some rule or set of rules we have accepted; i.e. tautologies and mathematics and they really tell us nothing outside of their contexts.

It seems to me that Descartes was pushing for metaphysical certainty, and I think it has been amply demonstrated that metaphysical certainty is impossible.

It seems to me to be a question of what we can logically doubt, — Janus

I'm not sure; it's more complicated than it looks.

Descartes doesn't start with, "The LNC is true; therefore . . . " He seems to place relatively little weight on the status of logical certainties. Indeed, he says that the evil demon could make us wrong even about "2+2 = 4". Would he agree, then, that his methodical doubt should exempt logical truths? Evidently not. "I think," for Descartes, has a certainty and an incorrigibility that "LNC" does not.

So if I say that the LNC is indubitable -- that it is not possible to doubt it -- Descartes wants me to explain this in the same way I would explain the alleged indubitability of perceptions, and he doesn't think I can do that. The evil demon holds sway not only over the physical world, but the logical world as well. (Once the demon's sway is broken, as the Meditations proceed, we can recover certainty about logic and much else.)

This raises enormous problems for the role of logic in Descartes' own method, of course.

That said, if we accept a rough equation of "What can be logically doubted" and "What it is possible to doubt," then yes, you've described the general level of doubt that Descartes is employing. He's using methodical doubt for a specific, highly unusual purpose -- a kind of metaphysical litmus test. As I wrote to @Ludwig V, there's a lot more to be said about why Descartes thought this would be so effective as a means of discovering certainty.

It seems to me that Descartes was pushing for metaphysical certainty, and I think it has been amply demonstrated that metaphysical certainty is impossible. — Janus

Hmm. Is the cogito meant to be an example of metaphysical certainty? Many philosophers do disagree that the cogito does what Descartes wanted it to, but to say it's been "amply demonstrated" is an exaggeration, wouldn't you say? Or perhaps you have some other level of metaphysical certainty in mind.

First of all, thank you to all participants in the ongoing conversation. Your input is greatly appreciated and it perfectly illustrates the different interpretations that I encountered while writing the OP. I am going to let you fine people continue your discourse along the multiple tangents that you are on. It is interesting to discover the landscape of reasoning that they reflect on.

Generalization is indeed a tricky business. I tend to regard it with deep suspicion, especially in the context of philosophy. The disagreement about certainty and uncertainty seems to me to be a case where generalization has generated a furious and false debate. It sweeps differences aside and makes them hard to see. No, I'm not saying that all generalizations do that. I am saying that some do, and it's not helpful. — Ludwig V

So this goes back full circle to the main intent of my OP. I wanted to show this tension between reality as it is and reality as we understand it to be.

Agreements are impossible without an alignment of understanding.
Understanding is impossible without generalizations.

I think you are right about the false debate generated by generalizations, because the whole debate is meaningless. There should be no disagreement about certainty and uncertainty, because they should not be treated as mutualy exclusive opposites. Rather they should be viewed as conceptual extremes that define a field of tension between them, like a spectrum.

It is "our job" to come to an understanding by finding each other on this field of tension. By taking the same position on this spectrum, we come to a shared understanding. It should be obvious that
this position is a volitile one, that will require continuous adjustment and refining to fit the pragmatic narative that lies at its foundation.

That's the popular summary statement of emotivism: "x is good" just means "hoorah for x," and "y is bad," just means "boohoo for y." As Hamlet says, "nothing is either good or bad but thinking makes it so." — Count Timothy von Icarus

Yes, I have seen it expressed that way. I don't think it does more than make an interesting beginning for a theory. Hamlet's version is somewhat different. I've always wondered where it came from - Shakespeare may have thought it up himself, but it is also likely that he read it somewhere.

Wouldn't the anti-realist position rather be that nothing is truly more or less desirable, that "desirable" just means "whatever we just so happen to currently desire." — Count Timothy von Icarus

Ah, I see. You are using "truly" to distinguish a realist concept from an ant-realist concept. In which case we are just talking about two concepts of desirability, and a concept is either useful or not, and never true or not. Yes. I'm dodging the question. That's because I don't know what I think (yet).

"better" just means "I prefer." — Count Timothy von Icarus

Well, it often means that, though, I would say, never just means that. See above.

So normally it is the claim that ends themselves cannot be judged better or worse, normally packaged with a denial of the rational appetites (the desire for truth and goodness themselves) so that even rather obvious ends like "not being lit on fire" must stem from a sort of arational sentiment/feeling (this being the result of the axiomatic the denial of rational appetites). — Count Timothy von Icarus

It all depends on what you mean by rationality. Conventional logic, as I'm sure you know, can't establish good and bad. But we can reason about good and bad, ends and means. Why would anyone want to deny that we desire truth (on the whole) and goodness (so far as we understand it)?

Hence, "truly better or worse" can still be used by some anti-realists. Different race cars can be truly better or worse; some are faster. You can have truly better or worse choices for which school you attend, which vacation you go on, etc.. It's rather the "moral good" that is denied. But the counter is that this "moral good" is incoherent, and that the topics of ethics is so bound up in practical reason as a whole that the denial of this new category doesn't actually secure anti-realism the way the anti-realist thinks it does, or at the very least is an inappropriate category for analyzing pre-Enlightenment ethics (Western and Eastern). — Count Timothy von Icarus

Now you have me puzzled. Why would anyone deny that we have a concept of morality, and of ethics?

Not wanting to endorse a position and arguing for positions that imply that self-same position are two different things, and thinkers often do both. — Count Timothy von Icarus

Yes. Sometimes, however, they do so because they think that position A does not imply position B. So I need details.

That, and that he contradicts himself in trying to have his cake and eat it too, like when he argues from an is to an ought re treating children well a few pages after arguing for the impossibility of such a move. — Count Timothy von Icarus

Fascinating. Could you let me have the reference so I can look it up?

I think we should take Descartes at his word when he says that he does not intend "methodical doubt" to be applied in daily life. His quoted words in the letter make that pretty clear, and Williams cites a number of other instances. — J

Oh, I don't doubt his sincerity and I do take him at his word. But his move removes doubt from its usual context, and especially it's usual consequences. So it is a bit like shaking hands without touching. It's a greeting, but not a greeting. Or pulling a punch. That's what gives force to Hume's complaint that radical scepticism (not that he mentions Descartes) has no consequences. One doesn't quite know what it means.

He wants us to take methodical doubt very seriously indeed, as a method of ascertaining what might constitute certain knowledge. I called this a kind of "giving the Devil his due" skepticism; Williams calls it "pre-emptive skepticism," meaning much the same thing. Descartes wants certainty, not merely what seems overwhelmingly likely. So he's willing to make enormous concessions to what a hardened skeptic might claim. — J

Yes, in one way I understand all that. Perhaps you could think of my obstuseness as an application of his method to his method. (Oh, I do hate arguments like that. Don't take me seriously).

See what I mean?

And there are a number of modern arguments, broadly analytic or Wittgensteinian in nature, that make that case. — J

Oh, yes. We could get them out of the books and see what we think of them. But improvising on the basis of an unreliable memory is also quite fun.

It's not that "I have two hands" must be shown to be indubitable, but rather that "whatever I affirm that I perceive clearly and distinctly" is indubitable -- that is, cannot, under any circumstances, be mistaken. So, with respect, this isn't quite it: — J

Now you are switching back to wholesale undermining of an entire class. We have ways of telling when our sense our misleading us (I prefer "telling when we have misinterpreted our senses"). How else does Descartes know that he has been misled in the past? This won't do at all.

I read him as asserting what is possible, not what is the case. It's the difference between saying, "That bird could be an oriole" and "That bird is an oriole." These are both assertions; if I make the first one, it will be true if the bird could be an oriole, and false if it could not be. The second assertion says something quite different; it will be true if the bird is in fact an oriole, false if it is not. I believe the former mode is what Descartes is talking about. — J

Yes. I get that. It is a common way of presenting sceptical arguments. I'm not sure it is actually in the text. But it might be. The trouble is that the presentation usually collapses possibility into logical possibility, and establish what are now contingent statements on the basis premisses that make them all a priori or analytic (cf. Euclid or mathematics in general). But if we want to eliminate all contingent statements from our knowledge base, we'll end up in a sad state, don't you think?

It's just that, in the absence of egregious oppression and lack of quality of life, this never seems to happen. — Janus

No, it doesn't. Most people don't care much about the big picture and just want to be left in peace. True, that can be a mistake, but it seems to me that's how it is.

I think you know from past discussions that I would be the last to indulge in human exceptionalism and conclude that we are somehow more than mere animals. We are only exceptional inasmuch as we are very unusual animals. That said, there are also many other very unusual animals. — Janus

Sorry. That remark was intended in general, not in particular. I write quite quickly when I finally get to the keyboard. Sometimes I don't put things precisely enough. But I've found that if I write too slowly, I end up not writing at all.

It seems to me to be a question of what we can logically doubt, and I think the answer is 'anything that can be imagined to be false without logical contradiction'. It seems we cannot doubt the LNC itself without falling into incoherence. — Janus

There's a good point there. If Descartes does try to doubt the LNC, the project will fall apart. Same thing if he doubts his memory. He makes quite a fuss about that at the end of the first meditation.

The obverse is what we can absolutely certain of; and I think that would be only what is true by definition or according to some rule or set of rules we have accepted; i.e. tautologies and mathematics and they really tell us nothing outside of their contexts. — Janus

Yes. That's a trap. The price of absolutely certainty is paralysis in the empirical world. But perhaps we don't live in the empirical world? If we want to return to normal life (a dubious prospect, but still..) we need to re-cast this conceptual space. That's what Wittgenstein is trying to do - and, in his way, Moore.

But his move removes doubt from its usual context, and especially it's usual consequences. — Ludwig V

Absolutely right. So I read you as saying, "There is only one good purpose to which doubt can be put -- its usual context -- and because Descartes is suggesting otherwise, it's unsatisfying, like shaking hands without touching."

But we can instead say, "This is why Descartes is a great philosopher, not just an interesting one. He believed he had found a whole new and important use for doubt, one that is precisely not its ordinary use. And the ramifications of his idea were so provocative that we've been discussing it ever since!"

Again, we'd need to really dig in to his reasons for "inventing" Methodical Doubt, and what he hoped it could accomplish. I'm willing, if you like.

But improvising on the basis of an unreliable memory is also quite fun. — Ludwig V

:rofl: Story of my life.

Now you are switching back to wholesale undermining of an entire class. We have ways of telling when our sense our misleading us (I prefer "telling when we have misinterpreted our senses"). How else does Descartes know that he has been misled in the past? This won't do at all. — Ludwig V

Yes, the doubt here is applied to the class, not individuals within the class. The "how else" question is largely answered by Descartes in terms of dreaming. He says he's been misled in a dream --and not known it at the time -- to such an extent that he thinks we have to take the possibility as real. But remember, the question is not "Did it happen?" but "Could it happen?" Of course you may feel it simply could not, but that's disagreeing about a result concerning what can be doubted, not the method itself.

But if we want to eliminate all contingent statements from our knowledge base, we'll end up in a sad state, don't you think? — Ludwig V

Yes! That's why Descartes is so concerned to win back all (or most) of the territory he concedes as uncertain. He uses doubt to demonstrate, in the end, a method by which we can learn what is certain.

But we can instead say, "This is why Descartes is a great philosopher, not just an interesting one. He believed he had found a whole new and important use for doubt, one that is precisely not its ordinary use. And the ramifications of his idea were so provocative that we've been discussing it ever since!" — J

Certainly we can say that. My arguing that he is wrong does not mean that I don't think he is a great philosopher (though it might mean that I think he is an even greater mathematician/physicist). His achivement is that he came up with a really interesting wrong idea - so interesting that it has dominated Western philosophy for over three hundred years. If I could achieve anything even close to that, I would be very pleased with myself.

Again, we'd need to really dig in to his reasons for "inventing" Methodical Doubt, and what he hoped it could accomplish. I'm willing, if you like. — J

OK. Hit me.
Lee Braver wrote a book called "Groundless Grounds" in which he argues that Wittgenstein and Heidegger both argue that a key part of their very different projects was to return philosophy from its obsession with the theoretical and derive its understanding from everyday life. I'm not scholar enough to know for sure, but I think he makes a very good case. That's why I'm going on about it.

He says he's been misled in a dream --and not known it at the time -- to such an extent that he thinks we have to take the possibility as real. But remember, the question is not "Did it happen?" but "Could it happen?" — J

Yes, he has been misled by a dream. But when he woke up, he realised the truth. It's that insistence on being absolutely certain now that creates much of the problem. These philosophers have no patience!
Suppose he told us that he dreamt he was an astronaut and flew to Mars last night. Are we to think it could have happened? And isn't the fact that it couldn't have happened the key reason why he, and we, are so sure that he dreamt it? And that is true even though it is not self-contradictory to assert that he did fly to Mars last night.

Of course you may feel it simply could not (sc. happen), but that's disagreeing about a result concerning what can be doubted, not the method itself. — J

In a way, you are right. I wouldn't seriously question the idea that, in a specific context, it might be helpful to re-examine one's assumptions. But Descartes' project is removed from any specific context, and it's target is everything he, and we, think we know. That's a very different kettle of fish - and that grandiose aim, to criticize everything is a typical philosophical over-reach.

People forget that something can be possible and not the case. It was possible that my parents might have lived to be a hundred years old. Yet I know that they didn't. Earlier, I gave as an example of something that is certain "I have two hands". That comes from G.E. Moore and Wittgenstein discusses it. It is a contingent statement, so it is, in theory, possible that I do not have two hands. But if I consider the idea carefully, it makes no sense; there is not the remotest actual argument for supposing that I do not have two hands.

Yes! That's why Descartes is so concerned to win back all (or most) of the territory he concedes as uncertain. He uses doubt to demonstrate, in the end, a method by which we can learn what is certain. — J

There are two moments in his project. Creating the doubt, and resolving it. I may be questioning the creation process, but, in a way, I am already participating in his project. There is another line available, which is to accept his project, and consider whether his retrieval is successful. Unfortunately, there is another vast literature on that. What's worse is that many since then have tried to rescue the situation. No-one's really put the issue to bed. It would seem that he achieved too much in the first phase and not enough in the second.
Of course, that may be because it has now become a standard exercise - no, initiation - for those beginning philosophy; no-one else, except Socrates, has achieved that. The two of them constitute the founding myths of philosophy. That's paradoxical, in a way; one of the founders of philosophy discovered that he knew nothing and the other unwittingly showed that it is not possible to know anything anyway. No wonder philosophy is a mess.