How is it that there are so many minds that are incapable of understanding mathematics? ... the skeleton of our understanding, ... and actually they are the majority. ... We have here a problem that is not easy of solution, but yet must engage the attention of all who wish to devote themselves to education.

The advance of science is not comparable to the changes of a city, where old edifices are pitilessly torn down to give place to new, but to the continuous evolution of zoologic types which develop ceaselessly and end by becoming unrecognisable to the common sight, but where an expert eye finds always traces of the prior work of the centuries past. One must not think then that the old-fashioned theories have been sterile and vain.

Doubt everything or believe everything: these are two equally convenient strategies. With either we dispense with the need for reflection.

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

Just as houses are made of stones, so is science made of facts.

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

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.