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.

All that is not thought is pure nothingness; since we can think only thoughts, and all the words we use to speak of things can express only thoughts, to say there is something other than thought is therefore an affirmation which can have no meaning.

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.

Guessing before proving! Need I remind you that it is so that all important discoveries have been made?

Geometry is not true, it is advantageous.

Mathematicians are born, not made.