In good philosophy, the word cause ought to be reserved to the single Divine impulse that has formed the universe.

You have not succeeded in your experiments, that is all there is to it.

Intuition is given only to him who has undergone long preparation to receive it.

I am on the edge of mysteries and the veil is getting thinner and thinner.

To demonstrate experimentally that a microscopic organism actually is the cause of a disease and the agent of contagion, I know no other way, in the present state of Science, than to subject the microbe (the new and happy term introduced by M. Sédillot) to the method of cultivation out of the body.

Science brings men nearer to God.

When you believe you have found an important scientific fact, and are feverishly curious to publish it, constrain yourself for days, weeks, years sometimes, fight yourself, try and ruin your own experiments, and only proclaim your discovery after having exhausted all contrary hypotheses. But when, after so many efforts you have at last arrived at a certainty, your joy is one of the greatest which can be felt by a human soul.