The mind, once expanded to the dimensions of bigger ideas, never returns to its original size.

A mind once stretched by a new idea never regains its original dimension.

A mind that is stretched by a new experience can never go back to its old dimensions.

The main part of intellectual education is not the acquisition of facts but learning how to make facts live.

The longing for certainty... is in every human mind. But certainty is generally illusion.

The mind of a bigot is like the pupil of the eye. The more light you shine on it, the more it will contract.