If it is true that there is no greater sorrow than to remember a happy time in a state of misery, it is just as true that calling up a moment of anguish in a tranquil mood, seated quietly at one's desk, is a source of profound satisfaction.

Sooner or later in life everyone discovers that perfect happiness is unrealizable, but there are few who pause to consider the antithesis: that perfect unhappiness is equally unattainable. The obstacles preventing the realization of both these extreme states are of the same nature: they derive from our human condition which is opposed to everything infinite.

An enemy who sees the error of his ways ceases to be an enemy.

Conquering matter is to understand it, and understanding matter is necessary to understanding the universe and ourselves: and that therefore Mendeleev's Periodic Table, which just during those weeks we were learning to unravel, was poetry.

To destroy a man is difficult, almost as difficult as to create one: it has not been easy, nor quick, but you Germans have succeeded. Here we are, docile under your gaze; from our side you have nothing more to fear; no acts of violence, no words of defiance, not even a look of judgment.

Nothing can be said: nothing sure, nothing probable, nothing honest. Better to err through omission than through commission: better to refrain from steering the fate of others, since it is already so difficult to navigate one's own.

The butterfly's attractiveness derives not only from colors and symmetry: deeper motives contribute to it. We would not think them so beautiful if they did not fly, or if they flew straight and briskly like bees, or if they stung, or above all if they did not enact the perturbing mystery of metamorphosis: the latter assumes in our eyes the value of a badly decoded message, a symbol, a sign.