You did not address the problem. Observing that a rock falls is not a reason for why the rock falls.

Sooner or later explanations reach a dead end — RussellA

What does this mean in terms of PSR? The observation that a rock falls is not a reason for or explanation for it falling. If explanation reaches a dead end then either we have failed to find the reason or there is no reason.

when "gravity" means no more than a rock falls to the ground when released. — RussellA

But gravity means more than that.

According to the original poster by reason he/she means explanation.

Are you claiming that there are reasons that do not involve explanations?

The OP describes the PSR ... — RussellA

From the OP:

In this way, the PSR is also called “Principle of Parsimony” or “Occam’s Razor”: the simplest explanation that accounts for all the data is the most reasonable one. — A Christian Philosophy

We posit three explanations — A Christian Philosophy

It depends on the meaning of "reason" — RussellA

In accord with the OP it means that there is an explanation.

Did you mean 'petitio principii', begging the question?

Thus, if all objects in existence are explained, by 1 of the 3 types of reasons as per the OP section "PSR in Metaphysics", then existence is also explained. — A Christian Philosophy

This is question begging.It assumes what is in question, namely whether everything in existence can be explained. These three types of reason are based on the existence of things. They do not explain why there is anything at all.

On the epistemology side, yes, that is, our knowledge of the PSR is defended by that premise. — A Christian Philosophy

Well, if we rejected the idea that there is a reason then we would not look for for one, but it does not follow that there must be one.

This occurs when we lack data. — A Christian Philosophy

That is the point. Where is the data that is sufficient to conclude that everything must have a reason?

Since there are only 3 types of reasons in the OP section "PSR in Metaphysics", the laws of nature would be explained by 1 of the 3 types. — A Christian Philosophy

Again, this is question begging. It assumes what is in question. It does not explain why there are laws of nature and does not demonstrate that those laws are prescriptive rather than descriptive.

C1 - The fact that my cat cannot understand The Old Man and the Sea does not mean that the book isn't understandable — RussellA

Maybe a superior intelligence might understand it, maybe not. In either case we do not, and based on our ignorance we cannot conclude that the universe is what we might regard as reasonable.

C2 - The fact that a question is the wrong question doesn't mean that there isn't a right question — RussellA

Sure, but the right question might lead to a rejection of the PSR.

C3 - The fact that every answer can be questioned doesn't mean that there isn't an answer. — RussellA

C3 - The fact that every answer can be questioned doesn't mean that there isn't an answer. — RussellA

I was referring to what you originally had as Parmenides conclusion, that the world has always existed. But your corrected conclusion is no better. Both are based on the wrong question (C2) - when did it come into existence? And (C1) - our inability to conceive how something can come from nothing marks a limit of our thinking, but should we assume that our limits are the measure of reality or possibility?

Parmenides pointed out that if the world had come into existence from nothing, there is no answer to the question as to why the world didn't come into existence earlier or later than it did. From this he concluded that the world has always existed (SEP - Principle of Sufficient Reason) — RussellA

The problem, as I see it, is the assumption that if one asks a question there must be an answer to that question. There are several conclusions that might follow from not being able to answer a question. They include the possibility that:

C1 - Reason and our capacity to understand is limited.
C2 - The question itself is the problem.
C3 - Any conclusion that follows is questionable.

Or if you mean "existence" as the general concept, then that's just a concept. Concepts are not concrete existing things that need reasons. — A Christian Philosophy

I mean the reason why there is anything at all.

The reason is given in the OP under the section "Argument in defence of the PSR". In short, it follows from the premise that "Reason finds truth". — A Christian Philosophy

A premise is the reason why there must be a reason for what is?

Although we do employ reason in our search for truth, it may lead us astray. Your example of swans is a good case in point. We might conclude that all swans are white based on the fact that all the swans we have ever seen are white, but there are black swans. Reason does not simply explain what is observed, observation finds truth.

You posit "laws of nature" as an explanation, but this is problematic for two reasons. First, we might ask what the reason is for the laws of nature. Second, what is the explanation for the causal power of these laws?

I don't think it dawned on any philosopher, before the advent of modernity, that the Cosmos - a word meaning 'an ordered whole' - could be anything other than rational. — Wayfarer

For Heraclitus the tension of opposites is essential. We may think of it is the function of reason to disambiguate, but logos holds opposites together in their tension. Logos does not resolve all things to 'is' or 'is not'.

Men do not know how what is at variance agrees with itself. It is an attunement of opposite tension, like that of the bow and the lyre.

(fragment 51)

We must know that war is common to all and strife is justice, and that all things come into being and pass away through strife.

(fragment 80)

In the Phaedo Socrates says:

One day I heard someone reading, as he said, from a book of Anaxagoras, and saying that it is Mind that directs and is the cause of everything. I was delighted with this cause and it seemed to me good, in a way, that Mind should be the cause of all. I thought that if this were so, the directing Mind would direct everything and arrange each thing in the way that was best. If then one wished to know the cause of each thing, why it comes to be or perishes or exists, one had to find what was the best way for it to be, or to be acted upon, or to act. On these premises then it befitted a man to investigate only, about this and other things, what is best.

(97b-d)

Socrates accepted Mind as the cause, but instead of inquiring about what Mind is, or how it arranged things, he sought an explanation for why it is best that things be the way they are. He did not find such an explanation in Anaxagoras or anywhere else. He thus launched his “second sailing” to find the cause. (99d). With his “second sailing” Socrates looks to what seems best in a double sense. First, he wants to understand how it is best that things are arranged by Mind as they are, and second, having failed to understand things as they are, that is, to attain truth and knowledge, he seeks what seems to be the best argument.

Mind or nous as the governing principle, arranging things according to what is best, is not the same as a world governed by reason.

For Aristotle, the question of the intelligibility of the natural world faces two problems, the arche or source of the whole and tyche or chance. We have no knowledge of the source and what happens by chance or accident does not happen according to reason.

“For every thing that exists, there is a sufficient reason for it to exist.” — A Christian Philosophy

What is the reason for existence?

What is the reason for thinking that there must be a reason for what is?

The ENEMY is the United States government. — ssu

Trumpian "conservatives" sound like the sixties counterculture. Perhaps the most significant difference is that the sixties movement was progressive, but Trumpism is regressive.

Do I understand you? — Moliere

For the most part, yes. He wanted to avoid accusations of heresy and atheism. He was, however, placed on the Index Librorum Prohibitorum, the Index of Forbidden Books.

In the first meditation he says:

So all I need, for the purpose of rejecting all my opinions, is to find in each of them at least some reason for doubt.

His reason for doubting is methological. That is to say, in the normal course of his life he does not doubt all that he now finds some reason for doubting.

So today I have set all my worries aside and arranged for myself a clear stretch of free time. I am here quite alone, and at last I will devote myself, sincerely and without holding back, to demolishing my opinions.

It is only now that he is alone and removed from the demands of life that he can call into doubt things that ordinarily he would be mad to doubt.

Would that happen today, no? — ssu

If Trump was asked : "Have you no sense of decency?" he would just smirk and say: "I have the most decency, the best decency. They say no one has more decency than me." It is, of course his complete lack of decency and his shamelessness that shields him from even being bothered by the accusation.

Do you think his conclusion—a kind of ontological argument for the existence of God—is also feigned? — Janus

Yes.

Or that his skepticism regarding the authority of the church extended to the 'holy book' itself? — Janus

He makes good use of the good book for his own ends. In Genesis 2 after man gains knowledge God says that man has become like one of us. God blocks them from eating of the tree of life and becoming one of them, that is, immortal. But Descartes, in agreement with the NT, says that the soul/mind is immortal.. The theme of being god-like is continued in the story of the Tower of Babel:

The Lord said, “If as one people speaking the same language they have begun to do this, then nothing they plan to do will be impossible for them.

(11:6)

In the fourth meditation Descartes says:

I know by experience that will is entirely without limits.

and:

My will is so perfect and so great that I can’t conceive of its becoming even greater and more perfect ... — Fooloso4

Once again we see what Trump means by MAGA, a return to the time of his mentor Roy Cohn and McCarthyism, a campaign of fear and repression, with the "deep state" now taking the place of communism as the enemy within.

You can infer ... — Corvus

You ignore what Descartes says and impose your own inference based on your own opinion rather than on anything said in the text.

How could he exist without his body and senses? — Corvus

A good question, but your rejecting the possibility does not mean that Descartes thought, even briefly, that is it impossible. Imposing your own opinions onto your reading of Descartes is bad practice.

He briefly doubts his own existence — Corvus

Where does he say this? He doubts his body and his senses, but not that he exists. He posits a malicious demon that will do everything he can to deceive him, but concludes it cannot deceive him about his existing.

He doubted everything even his own existence. — Corvus

He does not doubt that he exists. From the second meditation:

I will set aside anything that admits of the slightest doubt, treating it as though I had found it to be outright false; and I will carry on like that until I find something certain, or – at worst – until I become certain that there is no certainty. Archimedes said that if he had one firm and immovable point he could lift the world ·with a long enough lever·; so I too can hope for great things if I manage to find just one little thing that is solid and certain ...

Now that I have convinced myself that there is nothing in the world – no sky, no earth, no minds, no bodies – does it follow that I don’t exist either? No it does not follow; for if I convinced myself of something then I certainly existed.

My point was existence precedes doubting and thinking — Corvus

So you have said, again and again and again. I agree, but it is not as simple as you assume. It is not a matter of taking his side but of trying to understanding him. When you say:

Doubting one's own existence negates one's own sanity. — Corvus

you show that you do not understand him. He does not doubt his existence. That is the one thing he cannot doubt. That is his starting point.

One way to approach him is by attempting to read him as someone at that time might have. Belief in an immortal, immaterial soul was widespread and fundamental to the teachings of the Church. By substituting mind for soul reasoned thought rather than Church dogma and doctrine becomes fundamental. In addition, the unquestioned authority of Aristotle in matters of science is also called into question and replaced by certainty.

The question of whether consciousness is fundamental is an open question. We should not be too quick to dismiss Descartes because he held a similar view.

Right I agree but surely to be consistent Descartes must have imagined that he had grounds for skepticism regarding the existence of those other thinkers. — Janus

I don't think so. I think his doubt is rhetorical. A way to doubt the teachings and authority of the Church by feigning to doubt everything.

Added: Doubt is methodical, the purpose of which is to gain certain knowledge based on what is indubitable.

Is it not the case, that he must have existed in order to think? — Corvus

You are mixing tenses.

Existence is a precondition for thinking. — Corvus

It is a condition for thinking. Whether it is a precondition is not as obvious as you think. From Anaxagoras to the present there have been educated people who belief in the existence of a non-physical nous/mind/intellect/consciousness. In addition there have been and still are those who believe in the existence of a soul separate from the body.

All thoughts must have its contents or objects. — Corvus

Right.

When you say, a thinking being, it doesn't mean much without the knowledge of what the thinking is about. — Corvus

What is the point?

Without the content or object of the thought, Cogito is not saying much more than I dance, or I sing. — Corvus

Descartes concludes that he cannot doubt that he exists and cannot be deceived about his existing. He might be dreaming that he dances or sings but even if he is dreaming he is certain that he exists.

A person called "whoever" sounds still ambiguous. — Corvus

Whoever mistakes "whoever" for what a person is called is confused. This reminds me of how the Cyclopes is fooled by Odysseus.

These are the operations of mind which are only possible under the precondition of the living bodily existence. — Corvus

Right, sensing and willing are operations of the mind or of a thinking thing. You have made it clear that you think this requires a body, but this is not a good reason to misunderstand or misrepresent him, especially in cases where you are in agreement with him regarding the confirmation of your existence.

If the content of thought is empty or unknown, what meaning or relevance does the thought have with one's own existence on claiming cogito? — Corvus

That one is thinking and what is thought are not the same. He must exist in order to think.

Whoever is a name for nonexistence and unknown, hence meaningless. — Corvus

?

Isn't it a meaningless utterance? — Corvus

No.

I do exist. But my existence is confirmed by my own sense perception of the world of my own body and the actions I take according to my will. Not by cogito. — Corvus

In the second meditation Descartes says:

Well, then, what am I? A thing that thinks. What is that? A thing that doubts, understands, affirms, denies, wants, refuses, and also imagines and senses.

So you are saying thinking is the something that exists that is thinking, doubting and feeling? Saying that the "who" is Descartes really tells me nothing at all. — Janus

Although Descartes isolates himself in his room, as a thinking thing he is not isolated. As a thinking thing he is connected to thinking itself, that is to say, to what is thought not just by him but other thinking beings before and after him. The nature of thinking is something we do together, a joint project, something that occurs between human beings. The thinking self is not just the individual but thinking itself, which is by its nature public.

The point is even if you said, I think therefore I exist, it doesn't say anything about the content of your thought. — Corvus

But the content of his thought is not relevant to his not being deceived about his existence.

Whoever exists, exists is a tautology, therefore meaningless. — Corvus

I meant to say whoever thinks. You asked:

Who is "whoever"? — Corvus

in response to my saying:

whoever thinks, must exist, — Fooloso4

If all thoughts are strictly private to the thinkers, then your cogito is just a solipsistic utterance to me. It doesn't give any meaningful knowledge to anyone else. — Corvus

Do you exist? Could you be mistaken or deceived about this?

If that is the case, then he would have known the fact that he must have existed before thinking. — Corvus

The issue is not as clear cut as you seem to think. Consider the current idea of the existence of sentient matter, panpsychism, and the idea that consciousness is fundamental. In Descartes time and for some in our time as well, the soul is believed to exist independently of the body. I am not advocating any of these beliefs. My point is simply that we cannot appeal to "science" as if the matter is settled or conclude that Descartes was ignorant of science because he argues that he is essentially a thinking thing.

In addition, as I pointed out in my discussion with J, Descartes also says:

my whole self insofar as I am a combination of body and mind ...

My sole concern here is with what God has given to me as a combination of mind and body.

All of this makes it clear that, despite God’s immense goodness, the nature of man as a combination of mind and body is such that it is bound to mislead him from time to time. — Fooloso4

I'm guessing this was about religious doctrine, where plain speaking in a Catholic country could get you in trouble. — J

It think it likely that this is part of it. He did not want to suffer the fate of Galileo. But from a letter to Mersenne

...there are many other things in them; and I tell you, between ourselves, that these
six Meditations contain all the foundations of my physics. But that must not be spread abroad, if you please; for those who follow Aristotle will find it more difficult to approve them. I hope that [my readers] will accustom themselves insensibly to my principles, and will come to recognize their truth, before
perceiving that they destroy those of Aristotle.

.

Linguistic expressions are not thoughts themselves. — Corvus

Okay, but I don't see the point.

"Whoever thinks must exist" is a guess at best. It is not a logical statement. — Corvus

Can you explain how someone can think but not exist?

Who is "whoever"? — Corvus

Anyone and everyone who exists.

All thoughts are private to the individual who thinks. — Corvus

I don't see the connection with existence.

You sounded as if Descartes had no contemporary scientific knowledge at his life time — Corvus

To the contrary, he was on the forefront of science.

And my point to that was, that one's bodily existence is precondition to mental operations is not a contemporary science, but a very basic biological fact which could be even classed as a commonsense knowledge. — Corvus

Descartes uses the terms soul and mind interchangeably. There are plenty of people who do not lack commonsense who believe in the soul exists apart from the body.

He starts by saying:

I have a very good reason for offering this book to you, and I am confident that you will have an equally good reason for giving it your protection ...

and ends by asking for their help. He never gained their endorsement. Accepting his work is not the same as an appeal for them to change.

If he'd wanted freedom from the Church, that was easily available in nearby Protestant territory. — frank

Do you mean he could have avoided the fate of Galileo by escaping? Perhaps, but this would not save his writings from censorship by the Church. In addition, freedom of thought is not limited to his own thinking.

Descartes was clearly not on a quest to undermine the authority of the Church. — frank

Is that a fact or an opinion? Evidence?

Two different issues. One is Trump's criminal, unconstitutional actions. The other is what people voted for or against.

but this sounds more like a 19th century way of reading than 17th century. — J

None of the quotes are from 19th century authors.

To say in one's unpublished Private Thoughts that one "goes forth wearing a mask" surely speaks to the difference we all experience between our private and public selves, no? — J

I take going forth to mean not just a public persona but putting forth his writings.

Why would you think he was referring to his philosophical writings? — J

This thought remained private because unpublished. His advise to his student:

Do not propose new opinions as new, but retain all the old terminology for
supporting new reasons; that way no one can find fault with you, and those who
grasp your reasons will by themselves conclude to what they ought to understand.

This is a masking of one's opinion.

I suppose it depends on how you evaluate Descartes' status as a philosopher — J

Good point.

I'll just comment that you do this a lot. You come up with some weird subterfuge related to a famous philosopher and then announce your theories as if they're facts. — frank

My interpretation like any other is just that, an interpretation. Is your claim that Descartes wanted the Church to reform your own theory. If so, you do not announce it as such. If it is a fact, what is the evidence to support it?

Let's look at some facts:

From the Dedication to the Meditations:

For us who are believers,it is enough to accept on faith that the human soul does not die with the body, and that God exists; but in the case of unbelievers, it seems that there is no religion, and practically no moral virtue, that they can be persuaded to adopt until these two truths are proved to them by natural reason.

It is of course quite true that we must believe in the existence of God because it is a doctrine of Holy Scripture, and conversely, that we must believe Holy Scripture because it comes from God; for since faith is the gift of God, he who gives us grace to believe other things can also give us grace to believe that he exists. But this argument cannot be put to unbelievers because they would judge it to be circular.

But in its eighth session the Lateran Council held under Leo X condemned those who take this position, and expressly enjoined Christian philosophers to refute their arguments and use ail their powers to establish the truth; so l have not hesitated to attempt this task as well.

In addition, I know that the only reason why many irreligious people are unwilling to believe that God exists and that the human mind is distinct from the body is the alleged fact that no one has hitherto been able to demonstrate these points. Now I completely disagree with this: I think that when properly understood almost all the arguments that have been put forward on these issues by the great men have the force of demonstrations, and I am convinced that it is scarcely possible to provide
any arguments which have not already been produced by someone else.
Nevertheless, I think there can be no more useful service to be rendered in
philosophy than to conduct a careful search, once and for all, for the best
of these arguments, and to set them out so precisely and clearly as to produce for the future a general agreement that they amount to demonstrative proofs. And finally, I was strongly pressed to undertake
this task by several people who knew that I had developed a method for resolving certain difficulties in the sciences - not a new method (for nothing is older than the truth), but one which they had seen me use with some success in other areas; and I therefore thought it my duty to make some attempt to apply it to the matter in hand.

But although I regard the proofs as quite certain and evident, I cannot therefore persuade myself that they are suitable to be grasped by everyone. In geometry there are many writings left by
Archimedes, Apollonius, Pappus and others which are accepted by everyone as evident and certain because they contain absolutely nothing that is not very easy to understand when considered on its own, and each step fits in precisely with what has gone before; yet because they are
somewhat long, and demand a very attentive reader, it is only comparatively few people who understand them. In the same way, although the proofs I employ here are in my view as certain and evident as the proofs of geometry, if not more so, it will, I fear, be impossible for many people
to achieve an adequate perception of them, both because they are rather long and some depend on others, and also, above all, because they require a mind which is completely free from preconceived opinions and which can easily detach itself from involvement with the senses. Moreover, people who have an aptitude for metaphysical studies are certainly not to be found in the world in any greater numbers than those who have an aptitude for geometry. What is more, there is the difference that in
geometry everyone has been taught to accept that as a rule no proposition is put forward in a book without there being a conclusive demonstration available; so inexperienced students make the mistake of accepting what is false, in their desire to appear to understand it, more often than they make the mistake of rejecting what is true. In philosophy, by contrast, the belief is that everything can be argued either way; so few people pursue the truth, while the great majority build up their reputation for ingenuity by boldly attacking whatever is most sound.

He then asks for them to come to his aid by granting him their patronage. Rather than attempting to reform the Church, after asking for the help of the faculty he says:

The reputation of your Faculty is so firmly fixed in the minds of all, and the name of the Sorbonne has such authority that, with the exception of the Sacred Councils, no institution carries more weight
than yours in matters of faith; while as regards human philosophy, you are thought of as second to none, both for insight and soundness and also for the integrity and wisdom of your pronouncements.

He wanted the Church to reform, and he thought he could help it do that. — frank

Wouldn't the Church consider this heresy? Rather than reform the Church he attempts to reform man,

But all thoughts are private to the thinker. — Corvus

Not f he reveals them of makes them public.

Therefore your claim that whoever thinks, must exist, is false? — Corvus

I don't see how this follows.

Would you not agree it is a commonsense knowledge rather than a contemporary Science? Even ancient Greeks would have known about it. — Corvus

You asked about the scientific point of view, which is not the same as common sense knowledge. In any case, he cannot be deceived about his existence because he must exist in order to be deceived. As to whether he first exists and only subsequently thinks, he rejects this. He exists as a thinking thing. As such, it makes no sense to separate his existing and this thinking.

We see how conflicted Descartes is ... — J

I am not so sure. I ascribe to the idea that when a careful writer says things that seem contradictory that is is sign that we need to look closer and attempt to resolve the conflict.

He also clearly has trouble with using "mind" and "soul" interchangeably. — J

I think it is an intentional rhetorical strategy.

If his own nature is a "totality of things bestowed by God," surely this is the soul, rather than a thinking thing. — J

In the language of theology it is a soul, but in Descartes terminology a mind.

All these represent criticisms of Descartes on his own terms, pointing out contradictions or inconsistencies. — J

I am attempting to point beyond the contradictions and inconsistencies. It is part of his art of writing to conceal certain things that the attentive reading will attempt to make sense of. A few quotes from the
online appendix to Arthur Melzer's "Philosophy Between the Lines":

Descartes writes to one of his more imprudent disciples:
Do not propose new opinions as new, but retain all the old terminology for
supporting new reasons; that way no one can find fault with you, and those who
grasp your reasons will by themselves conclude to what they ought to understand.
Why is it necessary for you to reject so openly the [Aristotelian doctrine of]
substantial forms? Do you not recall that in the Treatise on Meteors I expressly
denied that I rejected or denied them, but declared only that they were not
necessary for the explication of my reasons?
– René Descartes to Regius, January, 1642, Œuvres de Descartes, 3:491-
92, quoted and translated by Hiram Caton in “The Problem of Descartes’
Sincerity,” 363

From the first paragraph of Descartes’ early, unpublished “Private Thoughts”:
I go forward wearing a mask [larvatus prodeo].
– René Descartes, “Cogitationes Privatae,” in Œuvres de Descartes, 10:213

Descartes took care not to speak so plainly [as Hobbes] but he could not help revealing
his opinions in passing, with such address that he would not be understood save by those
who examine profoundly these kinds of subjects.
– G. W. Leibniz, Sämtliche Schriften und Briefe, 2.1:506, quoted and translated
by Richard Kennington in On Modern Origins, 197

For example, here is Leibniz, reacting to Descartes’ seeming embrace of the view that all
necessary truths, like the principle of non-contradiction, are the product of God’s free and
arbitrary will:
I cannot even imagine that M. Descartes can have been quite seriously of this opinion….
He only made pretence to go [there]. It was apparently one of his tricks, one of his
philosophic feints: he prepared for himself some loophole, as when for instance he
discovered a trick for denying the movement of the earth, while he was a Copernican in
the strictest sense.
– G. W. Leibniz, Theodicy, 244 (2.186)

Whatever he recounts about the distinction between the two substances [mind and body],
it is obvious that it was only a trick, a cunning devise to make the theologians swallow
the poison hidden behind an analogy that strikes everyone and that they alone cannot see.
– Julien Offray de La Mettrie, Machine Man, 35

After corresponding with Descartes concerning the issue of whether animals were mere
machines, Henry More concluded that Descartes was “an abundantly cunning and abstruse
genius” who insinuated that mind as an incorporeal substance is a “useless figment and
chimera.”
– Henry More, Philosophical Writings, 184, 197-98

Thus one is right to accuse Descartes of atheism, seeing that he very energetically
destroyed the weak proofs of the existence of God that he gave.
– Baron d'Holbach, Système de la nature, 2:150, quoted and translated by Hiram
Caton in “The Problem of Descartes’ Sincerity,” 355

Does it entail then,
God thinks (doubts), therefore God exists? — Corvus

It does not entail that God thinks, but if God does think then God exists.

But that is not the case from the scientific point of view. — Corvus

No doubt that if Descartes has the benefit of contemporary science some of his views would change.

Is "I" extendable to other subjects such as he, she, you, it or they? Or is cogito strictly to "I" only? If it does, then could you say, "He thinks therefore he exists", or "It thinks, therefore it exists."?

If it is only for "I", then wouldn't it be just a solipsistic utterance?
— Corvus

Just realised that you have not answered to this question. What's your thought on this point? — Corvus

In response to your first question I said:

Whoever thinks, whoever doubts, whoever is subject to deception much exist.

With regard to the second question, if he were to have stopped there then yes.

I don't exist is untrue (not from cogito, but from my sensory perception), therefore it implies cogito is untrue as well. Agree? — Corvus

No.I must exist in order to have sensory perception. He does not doubt that he senses. What he doubts is the judgment that what he senses corresponds to anything outside his mind.

What is that something? — Janus

In terms of a what that something is thinking. In terms of a who it is Descartes.

He wouldn't have needed to displace the authority of the Church if that was his agenda. He could have just left and gone to live in Protestant territory. — frank

But Descartes' concern was not simply personal. It was to displace the authority of the Church from the mind of the thinking man,