Descartes did not prove he existed. He found something he concluded could not be doubted, that is, that he existed. He could not doubt it because he would have to exist in order to doubt. It does not follow that there is anything else that is indubitable.

But his real concern was to establish the foundations of knowledge, not to eliminate doubts that he did not have.

Mark Solmes corrected Descartes's deepity by pointing out "I feel - therefore I am". In his latest Theory on Consciousness he explains how our conscious state are realized by our emotions and how the rest of our mental properties(reasoning, symbolic language, pattern recognition, memory intelligence etc) introduce content in them.

Then let me prove I exist:
I am thinking (Minor premise).
Whatever thinks, exists (Major premise).
Therrfore I exist (Conclusion.)

Now, how do I prove that you exist?

That the room I'm sitting in, the country I live in, the world this country is part of, and the sun I saw today exist?

Now, how do I prove that you exist? — MikeB

The argument you presented for your existing cannot be utterly private without losing all meaning. Membership of a community is implied by your use of language.

That's interesting. Thank you. And I'd still be interested in anything you or anyone else has to say here.

If we assume that thoughts are different from what creates/controls/observes/thinks them, then we would have to assume that every mental object exists (as an entity in itself) even if they were entirely the product of one's thinking since they would be objects of thought which they could not be if they were the same as to which does the thinking, I think. I'd like to ask you if when you say "I am thinking" you consider yourself different from your thinking?

Hello Daniel. I'd appreciate it if you'd first answer my question. Is there any way you can logically prove that I exist, independently of you? If I don't shouldn't I be giving you whatever answer you want right now?

the best I can do right now is:

I am aware of many things
There are things that are not me (as in, I am aware I am different from them)
There are things that think which are not me, and which I am aware of
Whatever thinks, exists

I know they think because I interact with them, and I am not the interaction itself but a participant (I am aware I am different from the interaction) I interacts.

How about this as a syllogism?

Minor premise: Things of my making are less than I am.
Major premise: Things that are less than I am are in my control.
Conclusion: Therefore anything (and anyone) that exists outside my control is not of my making.

Would that prove I have my own independent existence?

Thank you Daniel. I think we're saying close to the same thing.

I'm curious though if you think you are different from what you think.

I'll get back to you on that Daniel. I'm too tired right now.

Hello Daniel. Sorry I didn't get back to you sooner, but I still don't really have an answer for you. I'm inclined to say "yes," the thinker is distinct from his thoughts, but I can't explain why. Do you think there's no distinction between you and your thoughts? And can you explain why?

Good question MikeB. Lets say we go with the idea that there are forces and objects beyond our control that aren't our body. Does that still prove that others exist? No. But, if you say, "I am a thinker," then if other people thought and could think that they were the thinker, then there would be other "I"s in the world.

Now would you specifically be able to know if they were thinkers? If your definition of "I" never expanded from, "the thinker that knows its thinking", then you could not. And Descartes wasn't leaving it at that either. His goal was simply to start with a foundation to build other knowledge from.

So, we could try a few ideas ourselves. We can't see in other people's heads to know if there is an I there right? Typically though we expand the definition of I to include other aspects of ourself. If a thing matches enough of those, we say, "That's a thinker too." Basing off of Descartes initial line of thinking, where would you go from there to prove that I exist for example?

I also believe my thoughts are distinct from me, can't really explain why clearly. All I can say with some confidence is that no matter where they come from or their nature, myself and my thoughts are not entirely the same thing, there exists enough differences between them that I am able to categorize them as distinct even if I cannot point the differences between them. Another way to put it is that even though I dunno what I am, I seem to easily grasp what I am not, and I could not not be something if there weren't more things besides me, I think.

Descartes proved he was here with "I think--therefore I am," but how would he have proved that he wasn't alone? — MikeB

I start by assuming that there is nothing external to my mind.
I have read and appreciated the greatness of Don Quijote, but cannot write a sequel of equal greatness.
As I was able to write Don Quijote in the past, but am not able to write a sequel, something must have changed.
My first supposition is that something has changed in my mind.
But then I read Great Expectations, which I know I must have written, appreciate its greatness but am still not able to write a sequel.
As it seems that nothing has changed in my mind, I can only conclude that something has changed outside my mind, concluding that I am not alone.