Proofs of the Euclidean [parallel] postulate can be developed to such an extent that apparently a mere trifle remains. But a careful analysis shows that in this seeming trifle lies the crux of the matter; usually it contains either the proposition that is being proved or a postulate equivalent to it.

This hypothesis (Parallel hypothesis) would not destroy itself at all easily.

I bought some books in order to learn the first principles of philosophy.

I understood that the will could not be improved before the mind had been enlightened.

My parents are private investigators for God's sake.

The first object of my endeavours was the means to become perfect and happy.

Yeah, my dad bought me a guitar when I was like 10, and I didn't really want it then.