To be an abstraction does not mean that an entity is nothing. It merely means that its existence is only a factor of a more concrete element of nature.

Each generation criticizes the unconscious assumptions made by its parent. It may assent to them, but it brings them out in the open.

Education which is not modern share the fate of all organic things which are kept too long.

The true method of discovery is like the flight of an aeroplane. It starts from the ground of particular observation; it makes a flight in the thin air of imaginative generalization; and it again lands for renewed observation rendered acute by rational interpretation.

The aims of scientific thought are to see the general in the particular and the eternal in the transitory.

Mathematics, in its widest significance, is the development of all types of formal, necessary, deductive reasoning.

The consequences of a plethora of half-digested theoretical knowledge are deplorable.