Certainty of Self-Existence

[Venryx]

One could argue that logic is based on the assumption that one's senses are somewhat trustworthy.

Exactly; nothing can be known for certain (*see my definition above), since all foundations depend upon something else.

[robertb]

That's true, I didn't define what I meant by certain.

This definition is fine for now: "Established beyond any reason to doubt; untouched by skeptical reasoning."

That works as long as you take your existence and the general reliability of your senses to be axiomatically beyond the reach of doubt and skepticism. Of course, anyone who refuses can't really make any claim about anything at all.

[Venryx]

That works as long as you take your existence and the general reliability of your senses to be axiomatically beyond the reach of doubt and skepticism. Of course, anyone who refuses can't really make any claim about anything at all.

Exactly; that's why, by that definition, nothing is certain! (every proposition can have a "reason to doubt" cast upon it)

[Teallaura]

Exactly; that's why, by that definition, nothing is certain! (every proposition can have a "reason to doubt" cast upon it)

Are you certain?

[Venryx]

Are you certain?

Certain in the sense most people define it, yes. (I'm strongly convinced of that statement, so I'm "certain" according to the definition most people use)

Certain in the sense I defined it above, no. (/There are reasons to doubt that statement, so I'm not "certain" according to the definition I gave above)

[apophenia]

This first point, I'm unsure of, so take it with a grain of salt. Any statement, knowledge or otherwise, presupposes a great deal of information that is not explicit in the statement. Jeff Hawkins gives the example of the story, "Jane saw a doggie in the pet store window. She wanted it." We don't needed it pointed out to us that she wanted the doggie, not the window. Our background knowledge fills in the necessary assumptions and inferences. In the 80s, IIRC, artificial intelligence researchers started a project of simply adding knowledge statements and inference procedures to a computer, with the idea that they would hit a tipping point at which the machine began to display intelligence. It didn't work.

Anyway, long intro for a short point, but I think to be correct, a statement of Descartes thesis would need to be restated as:

I think, therefore I exist [given what I know about existing].

It's that latter addendum which causes the problem, as it makes the statement circular. Is there a minimum set of knowledge and inferences with which you can construct a meaningful analog but which doesn't draw from experience or our beliefs about experience itself? I rather doubt it. Is this a useful result? I don't know. One area where the circularity may be problematic is in how one thinks of "to exist." I recently postulated to a person that if we exist as ideas in the mind of God, to say that we exist in the sense Descartes meant, or most mean, is, imo, equivocation. At minimum, we don't understand the "rules" of existing that way.


The second point I'd like to draw in is one Descartes could not have been aware of, yet even many people today don't realize (and many deny). Consciousness as implemented is not a unified, atomistic thing (an indivisible entity). It takes time for neurons to trigger and fire, it takes time for neural networks to "settle" and it takes time for different parts of the brain to communicate with one another. The conscious mind likely doesn't have a "now" except for the illusion of one that it creates for itself. This at minimum means that there is going to be a temporal gap between the impulses which give rise to the "I think" part of the statement, and the actual conscious thinking the "I think" part. In general, then, the consciousness of it lags behind the reality of it significantly. This opens the door for a variant of "last Tuesdayism". It's entirely possible to create a brain where the impulses from the original source of "I think" were created en route, just like the idea that God created star light already en route to earth. However, it's not necessary for the brain to have existed and been stimulated at the time/source of the apparent origin of "I think." So, because of the nature of consciousness, the "I think, therefore I am" is broken by the practical necessity of consciousness and cognition occurring as processes spread out in time. The "I think" may itself be a false memory.

[shunyadragon]

Exactly; nothing can be known for certain (*see my definition above), since all foundations depend upon something else.

The fact that nothing can be known for certain is a meaningless given in the absolute sense, and the old theist notion that 'all foundations depend upon something else' is also uncertain and based on assumptions that may not be true. 'Turtles all the way down and forever!'

Reasonable reliability of our senses and assumptions of existence including the 'Self' are in reality what we all do in understanding the objective physical world around us, regardless of what we may claim as to what is certain or not. It is a fools notion to try and separate the relative certainty of the 'Self' from the certainty of the intricately interlocked relationships of the between ourselves and the world around us.

[The Remonstrant]

I've heard it said that there's something we can each know for certain: "I exist"

Ben: "But how do we know that?"
Sam: "Because you have to exist to be thinking about it! As Descartes put it: 'I think, therefore I am.'"
Ben: "Oh, that's makes sense. I conclude that I must exist."

Even this^^^ relies on the validity of logic. How, then, can it be more certain than our trust in logic itself? (or at least a part of it)

To me it seems that no one can even be certain of his own existence, since that would be assuming that to think requires existence. (as undeniable as it seems, this is still an unprovable assumption, and therefore we still cannot be certain of our own existence)

I'm personally unconvinced of my or your existence (or Cowpoke's existence). What's most disturbing is that I find myself (whose existence is in question) to be disturbed by the very notion of my potential non-existence, which was brought up by you (whose existence I again question). You have possibly ruined my petty non-existent life. Damn you!

[Teallaura]

Don't worry - the problem doesn't exist. If you can't be sure you exist then there's little point worrying about whether or not you exist.

Mind you, pursued to it's logical conclusion you also stop worrying about eating, wearing clothes and how your breath smells...