Geometry is the art of correct reasoning from incorrectly drawn figures.

What is a good definition? For the philosopher or the scientist, it is a definition which applies to all the objects to be defined, and applies only to them; it is that which satisfies the rules of logic. But in education it is not that; it is one that can be understood by the pupils.

Sociology is the science with the greatest number of methods and the least results.

But all of my efforts served only to make me better acquainted with the difficulty, which in itself was something.

All great progress takes place when two sciences come together, and when their resemblance proclaims itself, despite the apparent disparity of their substance.

It is far better to foresee even without certainty than not to foresee at all.

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.