The only thing that can bring joy is work.

There are two men in each one of us: the scientist, he who starts with a clear field and desires to rise to the knowledge of Nature through observations, experimentation and reasoning, and the man of sentiment, the man of belief, the man who mourns his dead children, and who cannot, alas, prove that he will see them again, but who believes that he will, and lives in the hope – the man who will not die like a vibrio, but who feels that the force that is within him cannot die.

Did you ever observe to whom the accidents happen? Chance favors only the prepared mind.

There is a time in every man's life when he looks to his God, when he looks at his life, when he wonders how he will be remembered.

Without theory, practice is but routine born of habit. Theory alone can bring forth and develop the spirit of inventions.

If it is a terrifying thought that life is at the mercy of the multiplication of these minute bodies [microbes], it is a consoling hope that Science will not always remain powerless before such enemies.

After death, life reappears in a different form and with different laws. It is inscribed in the laws of the permanence of life on the surface of the earth and everything that has been a plant and an animal will be destroyed and transformed into a gaseous, volatile and mineral substance.