As to those impressions, which arise from the senses, their ultimate cause is, in my opinion, perfectly inexplicable by human reason, and 'twill always be impossible to decide with certainty, whether they arise immediately from the object, or are produc'd by the creative power of the mind, or are deriv'd from the author of our being. — Part III, Section V, p. 84

my chamber — Manuel

Indeed. It's why I was thinking we'd need to graph out the arguments, because they are sometimes presented in terms that other arguments will undermine.

I haven't spotted a similarly straightforward example in the Treatise, but there's this in the Enquiry:

This table ... preserves its existence uniform and entire, independent of the situation of intelligent beings, who perceive or contemplate it.

But this universal and primary opinion of all men is soon destroyed by the slightest philosophy, which teaches us, that nothing can ever be present to the mind but an image or perception, and that the senses are only the inlets, through which these images are conveyed, without being able to produce any immediate intercourse between the mind and the object. The table, which we see, seems to diminish, as we remove farther from it: but the real table, which exists independent of us, suffers no alteration: it was, therefore, nothing but its image, which was present to the mind. — Section XII, Part I

How does this argument work? Hume demonstrates that only perceptions are present to the mind, not objects, by showing that perceptions change when objects don't; but then he will later use the fact that only perceptions are present to the mind to argue that the hypothesis of double existence is insupportable, that we have no grounds for a belief in an object separate from our perceptions as their cause. — But then where does that leave this argument which originally established that only perceptions not objects are present to the mind? If we can't contrast the apparent extension of the table with its 'real' extension, then we have no argument at all. We have something vaguely of the form P → Q → ~P. Yikes.

And it happens all over the place, his description of his chamber being another example, and his simple reliance on his own identity.

(1) P → Q
"If the object of a knowing is an appearance, then the knowing is filtered."

(2) R → ~Q
"If the object of a knowing is an action, then the knowing is unfiltered."

(3) R → ~P
"If the object X of a knowing is an action, then X is not an appearance."

You were on the right track: like a modus tollens but there's a condition hanging over it in (2).

We can use "real" to differentiate in particular explicit cases - a real painting, a real foot, by understanding what the contrary is - a counterfeit painting, an artificial foot.

But some folk wish to contend that there is a way of using "real" that somehow goes beyond that, having no contrary. — Banno

Why 'having no contrary'? Or do you only mean in the 'pants' sense, deriving it's meaning from the contrary?

I mean, it's true that we're never going to predicate of some object 'imaginary', not in earnest, but only as a manner of speaking. The logical form of such a claim is just going to be '~∃xFx' which doesn't commit us to anything. We can comfortably say something like 'Unicorns aren't real but imaginary'; no one's attributing a property to something that also has the property of being a unicorn.

I think we would like to be able to say something like, "If something is a unicorn, then it doesn't exist," or maybe if you have a name, like from a story, "If Sheldon is a unicorn, then he doesn't exist." I guess we can stuff that directly into classical logic, but I don't think it's a very comfortable fit. It is, however, pretty straightforward to say that if something (or Sheldon) is a unicorn, then it (or he) is a member of class known to be empty, so that's a contradiction — and the conclusion is just that (say) "Sheldon is a unicorn" is false; we'll only need to go for "Sheldon is not a unicorn" if "Sheldon" is known to refer — if, say, Sheldon is a horse with a horn affixed to his forehead.

The class of unicorns can be as real as you (whoever you are) generally take classes to be; it just happens to be empty, but that doesn't mean there's any particular problem talking about it. And if we define 'imaginary' as 'member of an empty class', it ought to serve pretty well as an opposite for 'real' in that most general sense, and show up in arguments about where we'd want it to.

Oh yeah, and then 'real' in this general sense is 'member of a non-empty class'. Which is fine.

Bonus anecdote:

Story Robert Creeley tells — didn't happen to him but another poet, I forget who — that after a reading someone from the audience came up to ask our poet about something he read, "Was that a real poem, or did you make it up yourself?"

Here's another way: there can be, I think Hume thinks, nothing in the perception itself that would tip off the mind as to its origin or nature. Thus we have no surefire way of distinguishing veridical observations from hallucinations or dreams or optical illusions. Hume accepts the usual argument as a step toward considering perceptions only, however they appear to the mind.

So we still do not get at the source of individuation — Metaphysician Undercover

But Hume explicitly doesn't care.

Same page is where he says all these mental phenomena (perceptions, feelings, ideas, what have you) are 'on the same footing.' And he assumes they are presented to the mind as discrete, already individuated packets.

He is absolutely *not* going to say they are shaped by the mind, because that suggests there is something to be shaped, something that already has a distinct existence outside the mind. But he explicitly wants only to look at perceptions etc. insofar as they are dependent on the mind: for Hume they exist at the moment we are conscious of them, and that's it.

I mean, they're different in quantity, not quality. They're both cardinal numbers, just of different sizes.

Now there are transfinite ordinals, but you'd have to ask someone else about those.

There is such a thing as equivocation between two or more meanings or usages of a term, right? I repeatedly described countability in its non-mathematical sense of “able to be counted — javra

Except (a) you want specifically to talk about mathematical infinities, and there's prior art there you might as well become familiar with; and (b) the mathematical usage of 'countable' is actually something a lot like 'able to be counted', because listable.

I think what's throwing the discussion off is that we don't normally talk about the cardinality of a line except when we're considering it as a collection of points, the continuum, which is not countable. But that's not really measuring its length, different deal. If you have an infinite ruler marked off in centimeters, you'll be counting again.

Are the infinities of natural numbers and of real numbers two different infinities? — javra

Yes. The cardinality of the set of natural numbers is aleph-0; the cardinality of the set of real numbers is aleph-1, aleph-0 raised to the aleph-0 power. It is not known whether there is a size in between, but I think most mathematicians think not. Could be wrong.

The definitions can of course be questioned, but they are commonly established — javra

I warned you this would be trouble.

The usual way of using these words in mathematics is pretty straightforward. 'Countable' means there is a one-to-one correspondence between the set you have and a subset of the natural numbers, maybe all of them. So either finite, or 'countably infinite' like the natural numbers. We're talking about sets where you can write down the members in a list, even if that list goes on forever. 'Uncountable' is for bigger infinite sets. The real numbers, to start with, cannot be written down in a list that goes on forever, no matter how clever you are.

Obviously countable is nicer to deal with, because you can use algorithms that iterate (or recurse) their way through a list and you know that will get you not to the end but as far as you'd like to go.

(Also: Zeus could write out all the natural numbers in a finite amount of time just by doing the next one faster each step; not even Zeus could write out the real numbers in a finite amount of time. Lists are friendlier, even when they don't terminate.)

There is an issue around the individuation of perceptions.

There's that passage where Hume claims perceptions are exactly what they appear to consciousness as, etc etc, so he's basically claiming they are self-individuating.

* Here it is, p. 190

For since all actions and sensations of the mind are known to us by consciousness, they must necessarily appear in every particular what they are, and be what they appear.

It's easy to pass over that bit as just the usual empiricist sense-data talk, but without it he has no basis for claiming that our perceptions are interrupted.

Once you have a line, whether any other point in the plane is on it or not can be determined; it becomes an absolute yes/no question. Within a plane, every point is either on the line, above it or below, so the line perfectly bifurcates the plane. (Not for nothing, but given a line and a point, you figure out its relation to the line using a mathematical construction called a 'determinant'.)

There's also a sense in which a line, like any other function, gives a perfectly clear answer to how a segment of it can be extended: go on exactly like this.

It's altogether very well-behaved, and as sharply defined as, say, a triangle or some other sort of figure.

Hmmm. I was hoping you'd say you were okay with this example so we could compare it to another that you feel differently about.

Does it help at all to look at how mathematics handles this? Vaguely similar questions do arise in mathematics.

So, for instance, we say any two points in a plane determine a unique line. But if we go up a dimension, thus allowing that third coordinate to vary without bound, two points are not enough to pick out a single plane, and there are infinitely many planes that contain the line they determine. You need one more point, not on the line, to uniquely determine a plane.

Just an example. Mathematics does sometimes directly address how determinate its objects are, at least in this sort of sense, whether there's a unique solution, finitely many, infinitely many, etc.

Is this sort of determinateness any use to you?

Is there any property in taxicab geometry analogous to curvature?

Maybe the average distance of the intersections at which you turn from the impossible direct route. Not sure what the point would be, but it's interesting to think of taxicab routes as approximations of the direct routes that are unavailable. (Or vice versa.)

So for your question about the determinateness of mathematical infinities, you would say here that a line is I guess 'determinate enough' that we can pick it out as an object?

Ah, I see, you meant countable as a unit, as a line. Sure.

countable — javra

Just don't say that. It has a specific meaning in mathematics, and the length of a line is not countable in that sense.

Doesn't matter to whatever you're saying. Carry on.

I know so little about math, but I'm always eager to learn. — Real Gone Cat

Uh huh

we have indications of the existence of external objects, — Manuel

Do we?

I think it is true that, broadly, we take beliefs, our individual beliefs and the beliefs of others, as indicative of how things are, but we know that we cannot deduce P from anyone's belief that P. We can take a middle course and count the beliefs of others as evidence, but such a procedure is rarely available when considering your own beliefs. There are very specific circumstances where that's reasonable, but in general there's something illicit in counting your own beliefs as evidence of their truth.

What Hume says quite definitely is that we do embrace the principle of the existence of body. Can we count that as evidence of the truth of this principle? Hume presents arguments that the principle cannot be supported either by our senses or by reason. Does that mean he leaves open the possibility of an 'argument from instinct' or some such thing?

You represent the conceptions of external objects as being dependent on, or necessarily caused by, perceptions. This denies the possibility that a representation of external objects could be entirely fictitious, imaginary, created completely by the mind. — Metaphysician Undercover

Not what I intended at all. I was, I thought, following Hume's usage in using the word 'perception' to cover both impressions and ideas; so a perception is something present to the mind, of whatever source, a perceiving that is done 'by the mind's eye' we might say.

It's best that you give proper context to "continu'd existence". This is what is expressed by Newton's first law, the law of inertia. — Metaphysician Undercover

Here's what I think Hume is saying.

As I watch the birds flitting about in my front yard, I have an impression of a bird first here, then there, then there, as it moves from tree to tree. On a naive view, we might say there is a body, some force is applied to that body, and thus the body is caused to move through the air. We can see in the bird's flight inertia, which carries it along a certain path (modified by gravity and drag) until it flaps its wings again, adding a new vector which modifies its course, and so on.

Now consider me watching this: I have an impression of the bird; that impression is replaced by a different one with the bird elsewhere. Did my impression of the bird move? Of course not; I'm sitting on my porch and all my impressions of the bird are in the same place. Did my impression of the bird acquire an inertial force carrying it from one place to another? Perforce, no: my impression did not move; my impression had no such force applied to it.

Whatever connects my impression of the bird in one place to my impression of the bird in another place cannot be the same sort of physical law (inertia) that connects the bird being first in one place to its a moment later being in another. Newton's laws may apply to external objects that occasion my impressions (if there be such things) but they clearly do not apply to my impressions themselves.

I think it's a line of thought something like this that lies behind Hume's arguments. Habit, custom, instinct, imagination, association, all these sorts of things will fill, within the mental realm, the role that Newton's laws fill in the physical realm, laws that connect one event to another.

And of course once started down this path, it'll become clear that even belief in the existence of distinct and persistent external bodies is also down to the operation of such mental laws. Hume recognizes that it is the science of human nature that must underwrite all the other sciences, including Newton's physics.

Of course you can disagree with Hume; but can you make a case against his view?

For instance, Hume's view as I'm presenting it (not sure I'm getting him right) could be tweaked to more closely resemble relatively mainstream psychology: to claim some physical law governs the behavior of external objects is to describe our expectations about their behavior, which will for us just be particular sensory experiences and that's what we're actually predicting.

There's (not coincidentally) a similar perspective flip in the subjective account of probability (and thus of statistics).

So what's the critique of such views beyond mere disagreement?

Are you remaining within the chapter? — Manuel

Yeah, except for going back to Part II Section VI for the existence stuff.

I think that some of this may be alleviated once you get to the part in which he discusses the imagination. — Manuel

Some of what?

So far as I can see, he's still talking about our perceptions of the object, and then the problem is how do these perceptions tell us something about the existence and continuity of these objects ("body"), which "we must take for granted." — Manuel

Two points:

1. Something else conspicuous by its absence is the word "representation"; when he covers this material in the Enquiry he uses phrases like "perception or representation", but there's no such suggestion here. The word might be in there somewhere, but there doesn't seem to be much use made of the idea; the whole flavor of the account is causal, mechanical. Whatever 'occasions' (Hume's word) our perceptions, they appear from mind's point-of-view as sui generis.

2. Even if there are principles connecting objects to each other 'out there', beyond our minds, those principles apply to objects, not to our perceptions of them — thus we must have our own mental principles, which will apply to our perceptions, in order to conceive something like causality. Similarly, even if there are principles connecting the presentations of an external object to mind — namely, the distinctness and continuity of the object — it will do us no good: we need principles that will relate certain perceptions to each other.

Hume thinks we can analyze the principles governing the behavior of perceptions, but if there are analogous principles governing the behavior of external objects, we cannot know what they are and cannot analyze them. We might as well presume there are no such principles, it makes no difference.

Ultimately, Hume is trying to convince his perceptions that they are perception. — Richard B

As the above makes clear, I don't think so. I think Hume's idea is that it's irrelevant what the source of our impressions is; however they come to mind, they are now mental phenomena, and whatever principles govern the relations among mental phenomena must be mental principles, not such principles as we imagine govern the behavior of external objects.

He doesn't really need the tyranny of Nature here, does he? The sceptic is not admitting anything of any consequence. — unenlightened

I'm still unclear on this. All I've come up with so far is that Hume believes he must provide some explanation for our universal assumption that there are distinct, continuing, external objects. Whether it's true is just not at issue; we have no reason to believe it (he says) but we do, so he believes he must explain why we hold this unjustified view.

The idea of existence conjoined with the idea of any object makes no addition to it, but existence conjoined with the idea of any object adds everything to it. — unenlightened

I mean, it's clear that there's a difference between imagining there's a chocolate cake in the kitchen and believing there is. Hume has already dealt with that difference, earlier in the book. What else is there to say?

I've always thought the logical argument against existence being a predicate was convincing: an object existing and not existing must have the same properties, else existing is not what distinguishes them.

I'm not sure what good it is, but Hume's point that to imagine something is to imagine it existing — that's pretty interesting. It actually sounds plausible, but of course you can't tell the difference! It's a strange thought that undermines itself.

I am unsure whether the intention is to put the above passage into first order logic as it stands independently of Kant or into first order logic such that it agrees with Kant's philosophy. — RussellA

I understood the issue in the OP to be the logic of the quote, whether it's Kant or not. Everyone else seemed to assume it was Kant, so I did too. Maybe a mistake, but not relevant to the logical question.

I still find the quote pretty straightforward, but only if you're comfortable with the logic.

I cognize something x. Cognition is a higher level function of the brain. I can cognize about x both as an appearance and a noumenon. — RussellA

That may be, but in the quote given, there's no as-ing of the object of cognition.

(doesn't deny the conjunction of P and Q). Rather, it takes that denial for granted: — bongo fury

I did longer versions of this where I included it as a premise: 'If x is an appearance, then x is not a noumenon' — I think the conditional was all that was needed, not a biconditional, for what it's worth.

restatements of the original position -- if all cognition is of appearances, in that very case there can be no cognition of noumena (since noumena aren't appearances) — Moliere

Anyway, I think @Moliere has the right idea: there's no argument per se going on here, but an explanation of terms. Kant isn't establishing a result, just clarifying.

We often say things like this just to make clear what would and what wouldn't count as a counterexample, for instance: Either all cars are Toyotas, or there is something that is a car and is not a Toyota. It's not obvious to people who do don't do FOL all day that the opposite of a conditional is a conjunction, but it is. It sounds right, sure, but is it logically valid? Yeah, it is.

Is that what Kant is doing? Am I on the wrong track?

Either all cognition is cognition of appearance, in which case there can be no cognition of noumena, or there can be cognition of the noumenon, in which case cognition is not essentially cognition of appearance — KantDane21

Is he, for instance, arguing that cognition is essentially cognition of appearance? How could he be, since one of the disjuncts says that it isn't?

As I said, we could do this up more completely with predicates and quantifiers, we could even throw in some modal operators to cover 'essentially', but I think all that's overkill. It's a simple passage, and @KantDane21 was just a little confused about its basic logical form.

Now if we wanted to try to handle @RussellA's suggestion that there is 'cognition of x as F', and that's what's at stake here, that looks like the sort of thing classical logic is really crappy at. There's no 'as' operator because that suggests predicate interpretation, which suggests fiddling with the domain in the middle of an argument, which I guess you can do without going all dialethic, but what's the point? (I'm thinking of simple stuff like 'x is short for a basketball player but tall for a man'. You can give a semantics for 'short' and 'tall' relative to a population and thus allow someone to be short in one sense but tall in another, if that's something you really need.)

Another route would be to note that Kant is apparently making a point about cognition, rather than about which objects fall into the class 'noumenon' and which 'appearance'. So we could instead define type of cognition (again, awkward for FOL but doable), something like this:

If x is a cognizing, then x is an a-cognizing (that is, cognizing something as an appearance).

We could, again, do it all up with quantifiers, but in essence all we want to say is this:

Either all cognizing is a-cognizing, or some cognizing is n-cognizing.

And the intent there is to leave room for the same 'object' to be a-cognized and n-cognized. But it is still implied here that a-cognizing and n-cognizing are disjunct 'mental events' or types of cognizing.

And again I take it that the point of passages like this is just to clarify what the denial of the conditional would amount to logically, what we would need to show as a counterexample.

A = x is cognizable, B = x is a noumenon (and ~B = x is an appearance)

1. (A → ~B) v (A & B)
2. (A → ~B) v ~(~A v ~B)
3. (A → ~B) v ~(A → ~B)
True

Not sure what everyone else is doing, or what your P and Q lead to, but the argument is obviously right and I think this is the simplest way to formalize it. (We could do quantifiers and stuff, but it's really simple.)

My way is cleaner than yours because my sentential variables are really pretend predicates, just leaving off the variables. That means we don't stuff quantifiers (like 'all') into the variables.

The main thing is to render 'All F are G' as 'F → G'; that is, read it as 'If something is an F, then it's a G.'

The only other rules used were de Morgan's law to get from (1) to (2), and then the equivalence of P → Q to ~P v Q to get from (2) to (3). Or you can just recognize that if something is both A and B, that means being A doesn't imply not being B.

And then we're done, because (3) is a tautology, so (1) is valid.

2.6 is the section about existence, and it's only a couple pages. I quoted some bits.

One minor point maybe worth going back to is his use of the word 'specifically', also used in our section when recalling 2.6, when he denies that external existence can be taken as something 'specifically different' from our perceptions. I haven't checked, but I strongly suspect that word here means 'different in kind', 'specific' from 'species'. That's how I read his point, but I don't think I mentioned I was relying in part on this particular word.

So the argument begins

(1) Existence, external or not, is not something we have any separate conception of.

But then we get the other part:

(2) The notion of external existence cannot be taken as specifically different from perception.

That sounds like it's telling us what sort of thing something that doesn't exist is.

I think that means (1) is at least a little misleading as I've phrased it.

(2) is part of the larger claim that it's only perceptions in our mind, nothing else.

So if we have an idea of existence, it's that sort of thing, a perception; but (1) had already shown that existence itself is not a perception, but just something part of every perception, so in a way nothing.

(Some of the confusion here is just rhetorical. It's a pretty common move to say something doesn't exist, at least not as the kind of thing you think it is, not if we take it to be what you think it is, but it does exist, just as something completely different. We're keeping the name, but changing the meaning. Like that.)

But there is something else going on here, because Hume says our idea of external existence turns out to be different relations, connections, and durations that we *attribute* to perceptions.

So these are ideas *about* perceptions.

Thus instead of thinking some idea we have is of an object that we also think exists, we will have the perception or idea of the object and then *attribute* to that perception the properties that will be refuted in 4.2, distinct existence and continuity over time.

But attributing, like relating or associating -- these don't sound like perceptions but ways of handling or working with or acting upon perceptions. We can, in addition, have ideas about what we're doing when do this sort of thing, and Hume bundles some of these mental behaviors together and calls them our notion of external existence.

The status of these mental behaviors might be clearer if we look back at Part I where most of the basic machinery is laid out.

On the whole, I find your reading of him to be quite accurate — Manuel

I'm leaning on his actual words too much though.

I'm not absolutely certain I've gotten to the bottom of the arguments in 2.6

I should be clearer. I was only asking if my reading of Hume was plausible, not whether what he says was.

I do want to evaluate the arguments as we come to them, but only once we know what they are!

we do not know — Manuel

That really might be. I'm undecided.

Hume sets out to show that various beliefs we hold cannot be justified either by observation or by reason. But we do, nevertheless, hold these beliefs, and we hold them even once he has done as much as anyone can to demolish them.

Why we would hold reasonable beliefs needs no explanation; why we would give up unfounded beliefs needs no explanation; but why we would hold questionable beliefs and continue to hold them once shown to be groundless — that requires some explanation.

Certainly this talk of nature deciding for us does that. Much of 4.2 is taken up with showing how exactly it works, to make it plausible that this is 'just how we think', willy-nilly.

So perhaps my wondering 'what we get out of it', why nature would so order things, is misplaced. That nature does so order our minds is all Hume is trying to show.

Plausible?

nature has made this issue too important to leave it to us to decide if objects ("body") exist or no — Manuel

Yes, and that's a pregnant suggestion, not really substantiated yet — since I'm less than a page into the exegesis so far.

Nature has not left this [ the principle of the existence of body ] to his [ the sceptic's ] choice, and has doubtless [ ! ] esteemed it an affair of too great importance to be trusted to our uncertain reasonings and speculations.

That last phrase referring to the results of Section I, Of scepticism with regard to reason. There he argues that even doing mathematics is, roughly, a matter of believing you've done it right, and checking your work or having others check it can only raise your confidence that you've done it right, never guarantee it.

Again, all about the psychology. It's not that mathematics can't be trusted absolutely, but that mathematicians can't be! And so it is for all sorts of reasoning. That's how we enter Section II, having established that the sceptic must reason even knowing that he reasons imperfectly. We even get a twin of the point made here:

Nature, by an absolute and uncontroulable [ by us ] necessity has determin'd us to judge as well as to breathe and feel. ... Whoever has taken the pains to refute the cavils of this total scepticism, has really disputed without an antagonist, and endeavor'd by arguments to establish a faculty, which nature has antecedently implanted in the mind, and render'd unavoidable.

If we go back through Part I, we may find some encomium to reason, but I'm not going to bother looking: I think we can just say 'Newton'. Hume may never bother saying in so many words what value to us reason has, because I think in 1739 he would consider the value, indeed the triumph, of mathematics and reason, for which reason nature would instill reason in us, to be perfectly obvious. We may, as he specifically argues, be unable to ground our reliance on reason in reason, but it's clear what we get by this reliance.

Not so for the external existence of objects. There has been nothing yet to explain why nature implanted this habit in us, why the belief in external objects is so necessary. What do we get out of this belief of such great importance that nature implanted it in us?

We will have to be on the lookout as we go through Section II for some clue if not explanation, as to what this belief does for us.

It is curious that he treats reasoning (with the principle example being mathematics) and the belief in distinct, persistent, external objects as separate questions, albeit giving them related answers. In the post-Frege world, we might naturally think these go together. We carve up the world into classifiable objects to make it safe for logic; conversely we analyze the world using the logic of predicates and classes because we have carved it up into distinct objects with properties in common. Logic and objects go together. Without distinct objects, there is nothing for the functions of logic (not the predicates, not the truth functions, quantifiers, or other operators) to be applied to.

tis in vain to ask — Manuel

Good.

I think the warmup is done and now we ought to go right through and discuss the arguments as they arise. I've considered graphing them out, but it'll be more fun to make connections as we go.

I was going to start at the first proper argument, that continued and distinct existence are equivalent, but we should look first at the introductory bit, whence this quote comes, because there's some guidance there.

The sceptic, he says, "must assent to the principle concerning the existence of body ... Nature has not left this to his choice."

We may well ask, What causes induce us to believe in the existence of body? but 'tis vain to ask, Whether there be body or not? That is a point, which we must take for granted in all our reasonings.

Belief in the existence of body is
(1) not supportable by the senses or by reason;
(2) not a matter of choice;
(3) imposed on us by nature;
(4) caused.

Section II, then, takes as given the phenomenon that we believe in body; what we're looking for is a causal explanation of this belief. It will not turn out that we do not so believe, or even that we could, if we chose, not so believe. We do. The only question Hume is addressing is why.

Before explaining some fact, we need to be sure we know what the fact is, and this Hume has already done in Part II Section VI, Of the idea of existence, and of external existence. He will refer to those results almost immediately.

There it is claimed, first, that since to conceive of any thing is to conceive of it as existing, existence is not a distinct idea at all, not a separable perception:

That idea, when conjoin'd with the idea of any object, makes no addition to it.

Specifically what Hume is saying here is that we can have no idea of existence, an idea that we might join to another idea, as a way of having the idea of something existing. It's about our conceptions, not logic, not language. Might Hume have taken another line? Might he, for instance, have said, that to imagine an object differs from imagining it as existing in that the latter is more vivid, or more complete, or something like this? There would still, I think, be no distinct conception of existence. Even if he were to say that conceiving an object as existing is the usual conceiving but accompanied by some particular feeling, that leaves the conception the same, and this is Hume's only point.

But to say that we have no separate conception of existence, which we might add to our conception of an object, is not quite to say that the only existence objects have is in being perceived (esse est percipi). We can form no conception of the existence of an object; that's a fact of psychology, of human nature, the subject of the book, not a metaphysical fact regarding objects and their mode of existence.

But Hume does want to say more, so we get a further argument, which begins:

We may observe, that 'tis universally allow'd by philosophers, and is besides pretty obvious of itself, that nothing is ever really present with the mind but its perceptions or impressions and ideas, and that external objects become known to us only by those perceptions they occasion.

This would all seem to turn on the meaning of the word 'present': I see the book here by me, but the book is not present with my mind, only the perception it occasions; the book remains forever 'out there' beyond the boundary of my mind. A cordon is drawn around my perceptions: within is mind, without is world. The question for Hume is not what's out there or what isn't, but how we may conceive what's 'out there', the psychological question, and perceptions offer him the solid ground of his psychology.

Now since nothing is ever present to the mind but perceptions, and since all ideas are deriv'd from something antecedently present to the mind [ argued earlier ]; it follows, that 'tis impossible for us so much as to conceive or form an idea of any thing specifically different from ideas and impressions.

That is, when we try to conceive the 'external objects' that occasion our perceptions, we have nothing but perceptions to work with — we have no other material with which to construct a conception of 'object', no material that would make such a conception a distinct sort of thing from a perception.

Or: try as you may to conceive, for once, of an external object, itself, you will only produce another idea, an idea derived from previous perceptions, impressions and ideas. It's all your mind can do; there is only one sort of object available to your mind, a perception, and any attempt to bring some other kind of object, whatever it may be, into your mind will fail utterly or substitute an idea of that other kind of object.

There is no claim that perceptions are the only kind of objects, or that all objects are really perceptions, but only that the only kind of object in our minds is perception.

The farthest we can go towards a conception of external objects, when suppos'd specifically different from our perceptions, is to form a relative idea of them, without pretending to comprehend the related objects. Generally speaking, we do not suppose them specifically different; but only attribute to them different relations, connexions and durations. But of this more fully hereafter.

And that's the pointer to our section, Part IV Section II, where he will refer back to this section:

For as to the notion of external existence, when taken for something specifically different from our perceptions, we have already shewn its absurdity.

Note the same language, 'specifically different', meaning some kind of object distinct from the kinds of objects that can be within our minds, perceptions, impressions, ideas.


So how good is Hume's case? Are we convinced by Part II Section VI that external existence is not even an idea?

The introductory bit in 4.2 says we can't raise the question of external objects — because Nature — but we can look for causes of the belief we're stuck with.

But didn't 2.6 say we have, and can have, no such conception of the external existence of objects?

Isn't that a flat contradiction?

There's an out — because in 2.6 he says we don't, you know, really think of objects with external existence (since we can't) but that we do attribute 'different relations, connexions, and durations' to our perceptions.

4.2 is thus entirely about our perceptions, because Hume takes it he has already shown there's no point in trying to talk about anything else — or at least that such talk can be no part of his psychology. Thus, whatever idea we have about objects that exist distinct from our mind and perceptions, will be an idea about perceptions that exist distinct from our perceptions. Big no there. Whatever idea we have about objects that continue to exist when they are not perceived by the senses, will be an idea about a perception that continues to exist when there is no perceiving. Another big no. This is the substance of point (1) above, that neither the senses nor reason take us any way toward the principle concerning the existence of body.

So this is what nature has forced on us, the idea we think of as the external existence of objects, the bizarre belief that some our perceptions continue over time distinct from us the perceivers, since we can only think perceptions not objects. Picturing the tree is picturing the tree existing; picturing the tree existing when no one's looking is picturing the tree. Picturing the tree without the tree being pictured, is not a thing. Picturing yourself picturing the tree for a bit and then stopping, is picturing your picture of the tree waiting for you to come back and resume picturing it. Whatever we may try to think about external objects, this is what we'll end up thinking.

So it is clearly not knowledge or even justified true belief because the J clause fails. — Ludwig V

This is just to deny one of Gettier's premises. And that's fine, of course, but on what grounds?

Gettier is deliberately pretty vague about justification so that his argument applies to various formulations in the literature. He describes the evidence his protagonist has, with the assumption that it's the sort of thing we would usually consider adequate to justify holding a belief. If it's not, in our view, adequate, then we ought to strengthen the evidence until it is.

I take it as obviously true that we can have very strong evidence for a proposition that is false, for the simple reason that evidence is mostly a matter of probability.

In the case at hand, we have a farmer looking out at a field, and he's probably used to the way a cow standing in the field catches just a bit of light so that it's an indistinct bright spot in the otherwise dark field. He's never known anything else to be in the field that had this effect, though obviously a great number of things, including the cloth that turns out to be there, could, so when he sees such an indistinct bright spot he thinks 'cow'. That seems to me a perfectly reasonable belief and he has probably formed a true belief on just such a basis thousands of times before.

There is obviously a gap between the evidence and his conclusion; that gap has never mattered before, but this time reality falls into that gap. C'est la vie. You find the gap too large to allow him to claim to know there is a cow in his field; the point of the Gettier problems is to ask how small the gap has to be before you are willing to allow such a knowledge claim. If there has to be no gap at all, then it's a little unclear how useful the idea of 'justification' is. We may believe inference from empirical evidence can approach demonstrative proof, but we don't generally believe it can actually reach it.

Wherever size gap you choose to accept, even in a single case, that's where your situation can be Gettierized. That's my read. Rational belief is the sort of thing you have evidence for, not knowledge.



I find Lewis's contextualism a pretty obscure doctrine, so I'm not ready to go there yet, and I have more reading to do before taking on contextualism in general. Your view seems to be some sort of hybrid, in which knowledge is still a sort of justified belief, but what counts as justification is context-dependent. (Usually contextualism passes right by justification.)

For this case, Lewis might say that until that fateful evening when the farmer mistook an old shirt for a cow, the possibility of something making the same sort of bright spot in the field as a cow does was irrelevant, but it's not irrelevant for us as the constructors of the hypothetical, so we have to refuse to attribute knowledge to him. But now what? Must the farmer forevermore wonder whether the bright spot is a cow or an old shirt? Because we know he was mistaken once? We might well ask, but Lewis specifically does not make such demands on the farmer, who either will or won't. This is a puzzling theory, that the less imaginative you are the more you know.

What does seem to be the kernel of truth in this story is that — atomism incoming — some states of affairs are relevant to the truth of a proposition P, and some aren't, and some states of affairs are relevant to your knowing that P, and some aren't.

One of the roles of knowledge is to raise our standards of knowledge. I mean cases like this: suppose my son and I haul out the air compressor to inflate his car's tires, and then he's to put the compressor away in the shed. If I later ask him if he got it squared away, his report amounts to a claim to know that he did, and we can itemize that report: he knows to coil up the extension cord; he knows to bleed the hose, else it's too stiff to coil up; he knows to switch off the outlet it's plugged into or unplug it; but does he know to bleed the pressure from the tank? Did I even show him how to do that? If he didn't bleed the tank, then he only believes he put it away properly, but he doesn't know he did because a step has been left out, something relevant to the truth of "I put away the compressor properly."

That sort of relevance analysis, or contextualism, if that's what it is, I'd endorse. It does mean that the more you know, the more cases of putative knowledge might be excluded, because the world is rich with half-assery. But that's nothing like Lewis's acceptance of knowledge going bad when doing epistemology; I'm not imagining that the tank should be bled, I know it. And so it is with those benighted contestants on Deal or No Deal who claim to know the million dollars is in their case: they know no such thing; I know that they don't know not because I'm more imaginative, but because I know how random choice works, and they apparently don't.

Every instance, it seems to me we have a different perception — Manuel

This is another point he makes repeatedly, that we only have these unique, ephemeral perceptions, among which, to be sure, there are resemblances, but that neither reason nor observation justify us explaining these resemblances by positing a constant object they are perceptions of.

One thing notable by its absence in the whole section is conceptualization. Hume allows that one perception resembles another, but shows little interest in, or anxiety about, the sorts of conceptualization we worry about a lot. Hume's system is, to this extent, somewhat more mechanical and less cognitive, than we are used to in these post-Kant, post-Frege days. But it may indeed mean he is closer to mainstream psychology than we usually are; this is a naturalist epistemology.

Good point about the secret springs of nature.

There is something I find fundamentally unnerving about Hume's arguments, that they're hard to categorize as 'empirical' or not.

Will have more later, but I wanted to add what seems like a very strong argument against double existence -- though again it leaves me a little confused which arguments have priority over which.

This is the argument based on his account of our judgments of cause and effect being derived from the experience of constant conjunction. He argues that the claim that some object causes our perceptions cannot be accepted because we never have the opportunity to observe the object, on the one hand, accompanied by the perception, on the other, much less constantly.

That's an awfully strong argument *if* his account of causality is correct.

I have lots of rereading to do, and thinking after that, so I don't have a full picture of the argument yet.

I think the idea is that an impression is something that occurs to us, becomes present to mind, involuntarily, as feelings do, but is otherwise distinguished from an idea only in being more vivid.

In particular, we are counseled not to think we can distinguish impressions from ideas by their source, one external, the other internal. So far as mind is concerned, we are told, they are the same.

If that's right, then indeed the state description is right and the relation description is speculative.

It might seem to be only a formal shift, at one level, from something like (a) stuck-in(arrow, target), a relation, a function from an ordered pair to {0, 1}, to (b) stuck-in-target(arrow), a function from a single object to {0, 1}.

But the 1-place function is just a partially applied 2-place function. The target is just baked in.

Hume seems to think he doesn't need it, that you can coherently say 'impression' and dodge the question, "Impression of what?"

The argument goes round, that the hypothesis of 'double existence' is insupportable, which would be true if impressions are the same as ideas. But is that claim based only on introspection? Or does it arise from a methodological choice not to consider the 'what' that impressions are of? (Here I really have to reread.)

In the latter case, the methodological choice would end up becoming a substantive position, no double existence. Because of course by the time the question is addressed, there's no other answer you can give.

The starting point for Hume's position is that only perceptions (encompassing impressions, ideas, feelings) can be present to the mind.

A second point is that mind can be exhaustively described in terms of such perceptions and their relations (associations, resemblances, and the like).

Which is to say, the mind can be exhaustively described in terms of its states, by which we mean its 'internal' states, there being no others.

Is this plausible?

If a bee is perceiving a flower, isn't the most natural description of such a situation, that there is a relation, perception, that holds between bee and flower?

But Hume will take the bee to be in a perceiving state, full stop, rather than considering the bee as related to another object, the flower, in a particular way.

And the explanation for that move, from relation to state, must be found in Hume's account of the senses.

The question comes down to whether the main character's belief is justified or not; the stories create situations in which it isn't possible to give a straight answer. — Ludwig V

I think that's a pretty common reaction. "No false lemmas" can itself be taken as meaning that the belief in question wasn't really knowledge because it wasn't really justified, or as a fourth condition, separate from justification.

I find the whole approach suspect, as I think justification belongs with rational belief formation, where it's perfectly natural to consider the support offered by evidence as probabilistic, and the beliefs derived as partial. That leaves knowledge nowhere (as some would have it) or as a separate mental state, not belief that's really really justified.

But I'm open to argument that JTB-NFL can be made to work.

If justification and truth run on separate tracks, then justification can sometimes lead, quite reasonably, to falsehood, just as we can sometimes hold true beliefs by luck. (Lotteries provide the clearest examples for both: you can pick the winning number, without justification, and you can only be justified in believing that you didn't, given the odds, but you can't know it.)

"No false lemmas," by stipulating their conjunction, doesn't really address the main issue: either the true, justified lemma is knowledge, or it should face a Gettier case of its own — that is, you will be lucky that your premise is true. (If it's knowledge, then we've taken a step toward Williamson's E = K, the idea that rational beliefs are based on knowledge; but to claim that knowledge must be based on knowledge is either empty — because of course we'll take valid inference to be knowledge-preserving — or circular. If there's a third option, it's pretty subtle, but maybe there is.)

I'll admit, though, that it does seem to help. In Russell's example, checking the time from a clock that's stopped, had you looked a minute earlier or later, you would have formed a false belief, so you were lucky to have looked when you did. Now suppose that the clock was working and had the correct time, but stopped right after you looked; now I think we want to say you do have knowledge even though a minute later you would have formed a false belief. You were genuinely lucky in looking while the clock was still such that it was knowledge imparting.

So what's changed? If you look a minute later, we're exactly in Russell's scenario; a minute earlier, and you're fine. What if we compress things: suppose the clock stopped this time yesterday, briefly surges into life as you approach, just long enough to tell the right time for a minute or so, and then fails again. Now your window of luck is a range of a minute or so — too early or too late is still Russell, but for a brief span, the clock is knowledge imparting. Does that sound right? It sounds a bit dodgier now; you have been nearly as lucky as in Russell's scenario. The clock starting again feels wrong; had it started a minute earlier it would carry on being ahead until it failed, later and it would remain behind. What's missing is the clock actually being set; if a worker had just gotten the clock to work, and set the right time, you would again be acceptably lucky to look while it's keeping the correct time, even if it only did so for a minute before the worker cursed and set to work again.

To say that the clock has been set properly is to say that the time it displays is not only true, but justified, I suppose. But we can keep pushing the problem of luck back into these ceteris paribus conditions, which will grow without bound. Was the worker going by his own watch? What if his watch only happened to have the correct time? We're either going to continue demanding that truth and justification stay conjoined, or we're going to allow them to separate at some point, and that's the point at which Gettier will take hold.

Perhaps though what we're seeing here is that Gettier is the inevitable result of treating beliefs as atomic, and that the revenge cases are indicating that our beliefs never confront reality singly but as a whole, the Quinean view, I guess.

The mistake is to try and classify it as knowledge or not. — Ludwig V

The one thing everyone agrees on is that there is no knowledge here, so I wonder why you think there's a problem saying there is or isn't.

"No false lemmas" is discussed even on the Wikipedia page for the Gettier problem, in a section that begins with this amusing banner:

This article needs additional citations for verification. (October 2021)

Also on the SEP, which says

However, this “no false lemmas” proposal is not successful in general. — SEP

That's at least some places to start if you're sympathetic to the "no false lemmas" response.

He's saying, see, their using JTB and it failed to give knowledge. He's conflating one's claim to knowledge with actually having knowledge. — Sam26

This is not even in the ballpark of the Gettier problem.


For completeness, here's the IEP page on the Gettier problem.

So in this case, we can see that the proposed ideal, is really less than ideal, because the proposed inversion is contaminated by the presence of zero on the number line. — Metaphysician Undercover

Suppose you have a bag of apples you intend to give away.

There are two courses of action open to you:
(1) You can give someone the bag of apples, so that your hands are empty.
(2) You can give out the apples that are in the bag, and keep the empty bag.

There are two perfectly distinct results here: in one you have nothing; in the other, you have an empty bag. In both cases you have no apples.

It's understandable that you might not be inclined to say that a person who has no apples has a certain number of apples, namely 0. What you'd prefer is to say that they do not have any apples. There is no quantity that they have at all, and calling 0 a quantity is an abuse of the idea of quantity. That's understandable. The same with measurement: to say that a person who takes one step to the right has moved that amount is fine, but it is an abuse of the idea of distance to say that a person who has not taken a step at all has moved 0 steps to the right, to the left, whatever direction you like.

What justifies us extending concepts of quantity to include 0?

It's the bag, the difference between not having a bag at all and having a bag with nothing in it. 0 ends up playing a prominent role in positional number systems because the positions in such a number system are like bags laid out on a table into which you can put at most a certain number of items. But the bags are fixed; you do not remove them when they are empty.

Similarly, when we do algebra, we use containers for values, variables, and it may be possible for a variable to hold no value at all, that is, 0. But the mathematical functions we apply to a variable are defined so that they go through even if turns out the variable held a value of 0, or no quantity at all. You just have to follow some rules, so that you don't mistakenly divide by 0, which makes neither mathematical nor intuitive sense, as in this famous 'proof' that 1 = 2:

$\mathrm{Assume}\ a = b.\\\begin{align}a^2 &= ab\\a^2 + a^2 &= a^2 + ab \\2a^2 &= a^2 + ab \\2a^2 - 2ab &= a^2 + ab - 2ab\\2a^2 - 2ab &= a^2 - ab\\2(a^2 - ab) &= 1(a^2 - ab)\\2 &= 1\end{align}$

How does that apply to this poem in particular? — T Clark

To the Danielle Hope poem?

Not sure. I don't have any feel for how she writes.

Perhaps I shouldn't have made my remark about prosody sound so universal. Hebrew poetry, for example, is structured semantically, so there's a sort of rhythm of thoughts, rather than sounds. Or so I understand.

Williams I have some feel for, but the rhythm is the hardest part to analyze or explain. Reading "This is just to say" is like unfolding a bit of origami. He's very tricky about how the syntax is broken up over the lines; you unfold the next bit and it's satisfying but then you're not sure where to tug next and suddenly pop the next fold has come open. By the time you get to the very end and it's all laid out, you're not quite sure how you did it. Some of these little poems of his sound like they're sentences, sound urgently and insistently like sentences, but turn out not to be if you look carefully. Some of that is a commitment to spoken vernacular American, in which syntax can be a bit malleable, but some of it is the way lineation offers a competing structure, and that structure is in part rhythmic.