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

We also know how cruel the truth often is, and we wonder whether delusion is not more consoling.

Science is built up with facts, as a house is with stones. But a collection of facts is no more a science than a heap of stones is a house.

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

Einstein does not remain attached to the classical principles, and when presented with a problem in physics he quickly envisages all of its possibilities. This leads immediately in his mind to the prediction of new phenomena which may one day be verified by experiment.

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

It is often said that experiments should be made without preconceived ideas. That is impossible. Not only would it make every experiment fruitless, but even if we wished to do so, it could not be done. Every man has his own conception of the world, and this he cannot so easily lay aside. We must, example, use language, and our language is necessarily steeped in preconceived ideas. Only they are unconscious preconceived ideas, which are a thousand times the most dangerous of all.