A scientist's life, the author says, is indeed conflictual, formed by battles, defeats, and victories: but the adversary is always and only the unknown, the problem to be solved, the mystery to be clarified. It is never a matter of civil war; even though of different opinions, or of different political leanings, scientists dispute each other, they compete, but they do not battle: they are bound together by a strong alliance, by the common faith "in the validity of Maxwell's or Boltzmann's equations," and by the common acceptance of Darwinism and the molecular structure of DNA.

To accuse another of having weak kidneys, lungs, or heart, is not a crime; on the contrary, saying he has a weak brain is a crime.

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.

Human memory is a marvelous but fallacious instrument. The memories which lie within us are not carved in stone; not only do they tend to become erased as the years go by, but often they change, or even increase by incorporating extraneous features.

Today I think that if for no other reason than that an Auschwitz existed, no one in our age should speak of Providence.

Our ignorance allowed us to live, as you are in the mountains, and your rope is frayed and about to break, but you don't know it and feel safe.

Each of us bears the imprint of a friend met along the way; In each the trace of each.