Suicide may also be regarded as an experiment -- a question which man puts to Nature, trying to force her to answer. The question is this: What change will death produce in a man’s existence and in his insight into the nature of things? It is a clumsy experiment to make; for it involves the destruction of the very consciousness which puts the question and awaits the answer. Parerga and Paralipomena

If there were a distinguished person whose life, by birth and conditions, belonged especially to the same earthly dissimilarity, a distinguished person who would not assent to this divisive conspiracy against the universally human, that is, against the neighbor, if he did not have the heart to do this, if, clearly perceiving the consequences, he still trusted in God for the strength to bear these consequences while he lacked the strength to harden his heart ... the distinguished corruption would accuse him of being a traitor and self-lover—because he wanted to love the neighbor. Works of Love

I cannot agree with those who rank modesty among the virtues. To the logician all things should be seen exactly as they are, and to underestimate one's self is as much a departure from truth as to exaggerate one's own powers. The Adventures of Sherlock Holmes

One way to explain the complexity and unpredictability of historical systems, despite their ultimate determinacy, is to note that long chains of causation may separate final effects from ultimate causes lying outside the domain of that field of science. Guns, Germs And Steel