He lives well who is well hidden.
Few look for truth; many prowl about for a reputation of profundity by arrogantly challenging whichever arguments are the best.
I think; therefore I am.
The two operations of our understanding, intuition and deduction, on which alone we have said we must rely in the acquisition of knowledge.
Except our own thoughts, there is nothing absolutely in our power.
I know that I exist; the question is, What is this 'I' that 'I' know.