Experiment is the sole source of truth. It alone can teach us something new; it alone can give us certainty.

Pure logic could never lead us to anything but tautologies; it can create nothing new; not from it alone can any science issue.

Doubt everything or believe everything: these are two equally convenient strategies. With either we dispense with the need for reflection.

In the old days when people invented a new function they had something useful in mind.

If we knew exactly the laws of nature and the situation of the universe at the initial moment, we could predict exactly the situation of the same universe at a succeeding moment.

Doubting everything and believing everything are two equally convenient solutions that guard us from having to think

Astronomy is useful because it raises us above ourselves; it is useful because it is grand; .... It shows us how small is man's body, how great his mind, since his intelligence can embrace the whole of this dazzling immensity, where his body is only an obscure point, and enjoy its silent harmony.