We feel much happier and more secure when we think we know precisely what to do, no matter what happens, then when we have lost our way and do not know where to turn.

A little reflection will show us that every belief, even the simplest and most fundamental, goes beyond experience when regarded as a guide to our actions.

No simplicity of mind, no obscurity of station, can escape the universal duty of questioning all that we believe.

If I steal money from any person, there may be no harm done from the mere transfer of possession; he may not feel the loss, or it may prevent him from using the money badly. But I cannot help doing this great wrong towards Man, that I make myself dishonest.

When an action is once done, it is right or wrong for ever; no accidental failure of its good or evil fruits can possibly alter that.

An atom must be at least as complex as a grand piano.

The scientific discovery appears first as the hypothesis of an analogy; and science tends to become independent of the hypothesis.