Of Existence and Brains

Cogito, ergo sum!

Many of us are familiar with René Descartes' statement 'Cogito ergo sum' which is translated to 'I think, therefore I am'. Many of us take this as 'proof' of our existence, but it's not nearly that simple. First, we'll take a look at how he arrived at this.

Descartes arrived at this by systematically doubting everything that could be doubted and he could doubt no more. He realised that what he could not doubt was his own existence because to doubt his own existence, he would necessarily have to exist. Since he had set out with the building philosophy from the ground up, he took this as an axiom and said 'Je pense donce je suis'(Which is quoted verbatim from the Discourse on the Method), which is what I had quoted earlier in Latin and English.

Unfortunately, this statement is not logical inference of the existence of the self. Some of you must have already guessed the basic problem with this statement: The word 'I'.

Take the sentence, 'I think therefore I am'; I exist because I can think(and therefore doubt my own existence). But we are already presupposing the existence of 'I', making a statement about 'I' and then reaffirming that 'I' exists and that is a triviality. To think at all, one must exist in the first place!(Following Kierkegaard, Nietzsche and Russell)

Master of logical consistency

Now, one can actually go further and deny the existence of the self, but is it possible to deny thoughts? I'm not sure it is because even if you are a part of a larger consciousness, your thoughts being just images of that of something bigger and beyond comprehension, the thoughts still exist in some form. If we weaken the statement to 'Thoughts exist', the objection doesn't stand.

However, it is undeniable that there seems to be some truth to what Descartes says and his argument has definite intuitive appeal; it does feel right. So how do we go about justifying it?

The first step would be to stop treating 'I am' as a logical consequence of 'I think', but as a product of a process. The irrefutability of my own existence is a product of the process of my questioning it.

How? Let me say, 'I do not exist'. There's nothing logically wrong with the sentence, but there is something wrong with me stating it. For me to state this sentence, I would necessarily have to exist. If I try convincing you of the fact that I do not exist, by doing so, I am contradicting myself. This is an example of what Jaakko Hintikka calls an existentially inconsistent sentence. When you say 'I do not exist', you are not treating 'I' as an arbitrary quantity, but you are referring to yourself. When you make any self-referential statement, you necessarily acknowledge your own existence.

Who said old Finnish Logicians don't look cool? Jaakko Hintikka disproves!

But say all that exists are your thoughts and everything else is an illusion, what then? Isn't that a dead end too? Probably the simplest way to refute this is to rely on a principle that was championed by Bertrand Russell called Occam's Razor. This basically states that if there are two competing hypotheses, the one making less suppositions is the better hypotheses. It turns out that accepting reality as we perceive it requires far less suppositions than if we were to interpret these as illusions(Refer to Bertrand Russell's Problems of Philosophy).

But there's another approach to this problem and I'll explain it next:

"Your mind makes it real"

Let's modernise the setting, let's assume the I'm a brain in a vat which is being fed all sorts of information that corresponds to my senses by a computer. It definitely helps if you've seen The Matrix.(We're following Hilary Putnam's arguments).

Yes you are.

But first, let's consider a few things; If say, an alien from a different planetary system comes to Earth, sees our flora and draws a tree; without much objection, we can say that the picture does indeed refer to a tree. Now, say the alien has never been to Earth and draws a rather accurate picture of a tree quite randomly; can one say that the picture refers to an object or concept that it has never experienced before? According to Putnam, the answer is no.

This is what is termed as causal constraint and the principle is illustrated as follows:
'A term refers to an object only if there is an appropriate causal connection between that term and the object'

Now suppose a brain-a-vat(BIV for short) talks of 'trees'(note that the BIV cannot see a tree in your sense, and even when it talks of trees, it seems to speak because it's a brain in a vat -_- ), by causal constraint, it cannot be referring to a tree as we know it(and trees may not even exist), so what does it mean by the tree token? Putnam says that this can be one of three things:

1. 'Trees in the image' i.e. the experiences of the brain.
2. Neural impulses that stimulate the brain causing it to have experiences similar to those of a normal human while it sees trees.
3. The computer programme that is responsible for the stimuli and experiences.

   

   Trapped in a vat? Who you gonna call? Hilary Putnam!

Before Putnam, if the BIV had stated 'Here is a tree', it would have been taken that the BIV's token statement was false since we would have assumed that the BIV's token of a tree was referring to real trees. However, if we are to assign truth values to the BIV's statement on the basis of Putnam's assignments of possibilities, it would come out to be true. This is because its sentences express beliefs that are true internally in the brain's world. If you know no external reality, then what you experience is true inside your 'illusion'. 
Now, we are prepared to examine Putnam's arguments. Let us denote distinguish statements of the BIV from that of ours by suffixing the BIV's language with a '*'. 

1. Either I am a BIV(speaking vat-language) or I am not a BIV(speaking human language)
2. If I am a BIV(speaking vat-language),  then my utterances of ‘I am a BIV’ are true iff I am a brain* in a vat*.
3. If I am a BIV (speaking vat-English), then I am not a brain* in a vat*.
4. If I am a BIV (speaking vat-English), then my utterances of ‘I am a BIV’ are false. [inferred from 2. and 3.]
5. If I am a non-BIV (speaking English), then my utterances of ‘I am a BIV’ are true iff I am a BIV.
6. If I am a non-BIV (speaking English), then my utterances of ‘I am a BIV’ are false. [trivially, from 5.]
7. My utterances of ‘I am a BIV’ are false. [from 1., 4. and 6.]
8. My utterances of 'I am not a BIV' are true. [contrapositive of 7.]
9. My utterances of 'I am not a BIV' are true iff I am not a BIV
10. Hence, I am not a BIV

And as promised, I deduced that under certain assumptions, it is impossible to be a BIV. 

Contrary to what it might seem at first sight, this is actually one of the strongest critiques of metaphysical realism. According to the Stanford Encyclopaedia of Philosophy:

To metaphysical realism, the world is as it is independently of how humans take it to be. The objects the world contains, together with their properties and the relations they enter into, fix the world's nature and these objects exist independently of our ability to discover they do. Unless this is so, metaphysical realists argue, none of our beliefs about our world could be objectively true since true beliefs tell us how things are and beliefs are objective when true or false independently of what anyone might think.

If one were to subscribe to the position of metaphysical realism, he would be forced to admit the plausibility of a 'grand illusion' like the Brain-in-the-Vat thought experiment. However, Putnam showed that such a position is nonsensical even if we take the premises to be true.

Of course, there exist multiple counter-arguments and defenses of metaphysical realism. What is interesting to note is that Hilary Putnam himself was once a proponent of metaphysical realism. When he had published his critiques of metaphysical realism(the BIV experiment and the Model-Theoretic argument, which relies heavily on mathematical logic), he had changed his position to what he calls, Internal Realism. This internal realism resembles the metaphysics of Immanuel Kant on quite a few counts and has been termed as 'idealism in the guise of realism' by many. But it is beyond the scope of this essay to examine any of these.

References:

1. Key Philosophical Writings- René Descartes- Wordsworth Editions
2. Problems of Philosophy- Bertrand Russell- Oxford University Press
3. Cogito, ergo sum: Inference or Performance?- Jaakko Hintikka- Philosophical Review 71-1962
4. Reason, History, Truth- Hilary Putnam- Cambridge University Press
5. Stanford Encyclopedia of Philosophy- plato.stanford.edu