Of all things, good sense is the most fairly distributed: everyone thinks he is so well supplied with it that even those who are the hardest to satis… - René Descartes

But immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (cogito ergo sum), was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the philosophy of which I was in search … I thence concluded that I was a substance whose whole essence or nature consists only in thinking, and which, that it may exist, has need of no place, nor is dependent on any material thing; so that ‘I’, that is to say, the mind by which I am what I am, is wholly distinct from the body, and is even more easily known than the latter …

Except our own thoughts, there is nothing absolutely in our power.

When I turn my mind's eye upon myself, I understand that I am a thing which is incomplete and dependent on another and which aspires without limit to ever greater and better things...