Dubito ergo cogito, cogito ergo sum – Rene Descartes
("I doubt, therefore I think; I think, therefore I am)

Descarte's philosophy of dualism - the mind and the body are distinct, the brain and mind separate - has become a core belief of Western life, to the extent that the medical model of mental health had a hard time convincing people that biology might have anything to do with behaviour - witness the early success of Freud, whose psychoanalysis relied upon biology being, at least, irrelevant (sadly, when the medical model did triumph it forgot about the mind in its focus on the brain, and keeps putting pills into people whose life is going to continue to suck no matter how happy they become about it).

Immanuel Kant was a real piss-ant
who was very rarely stable
Heidegger, Heidegger was a boozy beggar
who could think you under the table
David Hume could out-consume
Schopenhauer and Hegel
And Wittgenstein was a beery swine
who was just as sloshed as Schlegel

There`s nothing Nietzsche couldn`t teach ya
`bout the raising of the wrist
Socrates himself was permanently pissed

John Stewart Mill of his own free will
on half a pint of shandy was particularly ill
Plato they say could stick it away
`alf a crate of whisky every day
Aristotle Aristotle was a bugger for the bottle
Hobbes was fond of his dram
And Rene Descartes was a drunken fart:
`I drink, therefore I am`

Yes, Socrates himself is particularly missed
A lovely little thinker but a bugger when he`s pissed

Monty Python, Bruce S Philosophers Song