Absolute space, that is to say, the mark to which it would be necessary to refer the earth to know whether it really moves, has no objective existence.... The two propositions: "The earth turns round" and "it is more convenient to suppose the earth turns round" have the same meaning; there is nothing more in the one than in the other.

Ideas rose in clouds; I felt them collide until pairs interlocked, so to speak, making a stable combination.

The aim of science is not things themselves, as the dogmatists in their simplicity imagine, but the relation between things.

[T]he different branches of Arithmetic - Ambition [G]eometry is not true, it is advantageous.

It is not order only, but unexpected order, that has value.

If we ought not to fear mortal truth, still less should we dread scientific truth. In the first place it can not conflict with ethics? But if science is feared, it is above all because it can give no happiness? Man, then, can not be happy through science but today he can much less be happy without it.

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