Sum ergo cogito? 1 nng
Following Descartes but in the opposite direction:
I exist. Something has made the assertion in the previous sentence and must have thought it to do so. Therefore my thoughts exist.
Combining with the direction established by Descartes I have cogito ⇔ sum. Since assuming either is equiavlent to assuming the other I conclude that Descartes does not establish existence as following from something more basic or fundamental. Instead he has merely stated a tautology.
Am I right or wrong? Or both, or neither?
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2"I exist, therefore something has made the assertion" is fallacious. Existence needs nobody's assertion of it. The inference is made from the act of assertion, which is not contained in "I exist". Otherwise, what is to be inferred is already assumed. Descartes's direction is also fallacious, see Could 'cogito ergo sum' possibly be false? But biconditionals need not be "tautological", many non-trivial theorems of mathematics have this form. – Conifold yesterday
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Does a rock think it exists? Well maybe, but it lacks the apparatus to communicate (with us), as such rocks cannot manifest their thoughts in a way that would convince us they exist. So the question becomes do believe that thoughts are immanent to all matter? Or do you believe that a certain level of structural complexity is needed to sustain thinking? The latter case would of course only allow for Descartes' "direction". – christo183 yesterday
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4Years of teaching provides clear evidence that sum does not imply cogito. – Servaes 22 hours ago
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I second the Servaes' motion. And the conditional is NOT the same as the biconditional to be sure. – J D 20 hours ago
4 Answers
Does thinking imply existing? Descartes argues yes: it is impossible for anything to think which does not exist.
Does existing imply thinking? Most people would say no. Most would say that a rock exists, and the rock does not think. Therefore it is possible for something to exist which doesn't think.
As such, the basic claim doesn't go both ways.
Meanwhile, your formulation wasn't quite what you described in the explanation. You should instead have said something like "I claim to exist. Therefore I think." That one is more defensible, depending on the exact definition of the verb "to claim." (Of course that is also not reversible: it is possible to think and just never say "I exist.")
Now, let us suppose instead that the statements, without any additional premises, did imply one another. Does that mean that Descartes was just stating a tautology? The simple answer is no, because he did not follow it round in a circle.
Suppose someone says "Alice is my daughter, therefore I am her parent." Similarly they could say "I am Alice's parent, therefore she is my daughter." If they said nothing else, that would be an unsupported circle (although not a tautology; being a tautology would require that it be impossible to not have a daughter called Alice)
However if they start with "I gave birth to Alice and remember it well!" then they can justify the other statements.
Similarly even if Descartes did hold that existing implies thinking, as long as his reason for saying "I think" is not "I exist" then he can use it as a premise.
Perhaps what would work is cogito ⇔ cogito sum, that is, "I think if and only if I think I am". Although someone who thinks may not think of asking themselves whether they are or not, if someone asked them whether they were or not I imagine they would not deny that they are.
Having a biconditional is not what makes a tautology. All one needs is a proposition that is always true regardless of the truth values of the component, atomic propositions. For example, let C be "I think" and S be "I am" then "C → S" is "I think therefore I am". The following is a tautology that is not a biconditional and it seems to represent the idea behind Descartes' idea:
I think, and since my thinking implies that I am, therefore I am.
Or symbolically, (C ∧ (C → S)) → S. To see that this is a tautology, even though it is not a biconditional, consider the following truth table:
Note that for all true-false valuations of the atomic propositions,C and S, the proposition being considered is true.
Michael Rieppel, Truth Table Generator. https://mrieppel.net/prog/truthtable.html
If you say "I exist", then you are thinking. It is that thinking that makes you sure you exist. That was Descartes point. Changing the order of the words of his thoughts doesn't make your thoughts any less thought-ish.
Do you think while asleep? Or under general anesthetics? If not, do you cease to exist? If you cease to exist, how come something happened to you during that operation?
So logically, your definition of "thinking" apparently includes whatever happens in those states, because you assume continuity of being (otherwise things get really complicated). So your "thinking" does not require consciousness, which is a contradiction.
The reverse argument by Descartes does not have this problem. It does not make an assumption about the state of being under the condition of non-thinking. It is flexible enough to grant existence to non-thinking entities as well, or at least the possibility of existence.
"the fact that I think proves that I exist" does not create a contradiction when any of its terms are reversed.
"the fact that I exist proves that I think" does, because while this does describe the normal state, there are states of existence, even for you, where no common use of the work "think" applies.
