While Descartes considered himself a staunch Catholic,

[MineralMan]

He did not ever write:

"Je crois, donc je suis." (I believe, therefore I am.)

Instead, he wrote:

"Je pense, donc je suis." (I think, therefore I am.)

He used the French phrase, rather than the Latin, "Cogito ergo sum," in one book, but used the Latin phrase in later writings.

He, better than just about anyone, understood the difference between "thinking" and "believing." As a champion of the use of reason to work things out, he knew that "beliefs" were often a bar to understanding, which required extensive "thought" and reasoning.

René Descartes was very precise in his use of language, because word choices are crucially important to understanding. He would be the first to ask someone:

Quoi, exactement, croyez-vous?

[struggle4progress]

1. The argument "cogito ergo sum" must actually be somewhat along the lines

"I am conscious therefore I exist"

The argument for it seems to be: "If I didn't exist, I couldn't be conscious of wondering whether I existed or not. But I am conscious of wondering about that. So by reductio, I must exist"

When phrased so, the argument appears to entirely private and without probative public value; but viewed in this way, it becomes a strange argument, for it is cast in words, which are a social phenomenon, used to communicate with other entities

Since to make his argument, Descartes must rely not only on the fact of his own consciousness, but also on his self-awareness of his own consciousness, perhaps his argument might more accurately be cast as "That I am aware, of my own confusion over the question of my own existence, shows that I exist"

Even with this gloss, the argument remains strange, since it involves choosing between "existence" and "non-existence"

Clear notions about the proposed category of non-existent things might be difficult to produce, without first having good examples of non-existent things to study carefully. Descartes, of course, could have considered in more detail the question of his own non-existence: "Suppose I do not exist. Then I know of at least one non-existent thing: myself" and so perhaps could have formed a clearer notion of non-existent things from that potential example, but the record seems to be silent on that

Another way, to study the proposed category of non-existent things, might be to understand what properties something must have, in order to fall into the category of existent things, but again one needs good examples (this time of existent things) to study, in order to understand what properties something must have in order to exist. This approach should have been possible investigative technique for Descartes, if he knew of anything that he was sure existed. But it would have been difficult for him, if he was unsure of the existence-status of every single thing, including himself: in that case, a pragmatic way to proceed might simply be to pick one particular thing (about which he knew something) -- such as himself -- and to define "existence" so that one particular thing "existed," then move to other more interesting questions

Viewed this last way, the solution he actually choose might effectively reduce to the assertion that every conscious thing exist. Of course, then it might still be true that not every self-aware thing will accept an argument purporting to showing that its own self-awareness implies its own existence: for following the same route, it might be equally pragmatic to pick one particular thing (about which one knows something) -- such as oneself -- and to define "existence" so that one particular thing "does not exist" before moving to other questions

[MineralMan]

2. Thinking is different from being conscious.

Cogito and Je pense describe active thinking, not mere consciousness. Reasoning, if you will, because that is what thinking is. Descartes used words extremely well. I recommend that you read some of his writings, even if only in an English translation. I wouldn't try to overthink what Descartes wrote. He used the precise words that expressed what he wanted to say. The Latin root is used in English in the verb "to cogitate," which means to think something over or to think through something.

Thinking is easy to understand. Thinking is purposeful and moves. Consciousness is just a state. I've read a good deal of Descartes' writings. He's far smarter than I am, and probably smarter than both of us put together. He's one of the great geniuses of civilization. Read him. Don't try to figure him out without doing that, please. You'll just look silly.

[struggle4progress]

3. I can only hope you are aware of the irony of suggesting that we should not overthink

an argument that a man once actually gave for believing in his own existence!

It is, of course, true that Descartes here appears to believe that he has reached the limits of his own ratiocination, since he apparently regards this argument as irrefutable and probably would not allow himself to be swayed on the conclusion by any further argument, no matter what premises such an argument might be founded upon and no matter what clever techniques were involved. But perhaps that merely means he already considered the conclusion to be true, in which case the implication might regarded as true (using, say, material implication)

On the other hand, it may not be entirely transparent what his argument actually hopes to reflect

If, for example, you want to interpret "think" as reflecting logical process, then you seem to commit yourself to the view that Descartes believed the argument was good at least as far as he believed himself to be a logical thinker. I do not know Descartes views on that topic, beyond the fact that he must have worried some about the potential quality of his thought, given the efforts he made to straighten his thinking --- but if he distrusted his own thinking, then we should ask what effect that might have on his assent to Cogito assertion

Another approach might be to consider the possible impacts of alternate translations of the verbs. "Cogitare" (say) has other senses, such as "ponder," "wonder," or "imagine." Perhaps, then, Descartes could validly say "I wonder therefore I am"? The Collier French-English dictionary online gives "believe" as a possible American English equivalent of the French "penser." I suspect most people would regard "I (---) therefore I am" as a valid statement for many verbs in the blank

In any case, the Cogito assertion is given as the dead-end of a thinking process, rather than the beginning. The subsequent method adopted by Descartes is a more limited critical skepticism: he is willing, at any time, to inquire into anything specific, but he limits his inquiry into one matter at a time