The sole function of education...[is] to open the way to thinking and knowing, and the school, as the outstanding organ for the people's education, must serve that end exclusively.

I believe that a simple and unassuming manner of life is best for everyone, best both for the body and the mind.

The greater the doubt, the greater the awakening

Only a very dull man spells a word the same way twice.

Fantasie is belangrijker dan kennis, want kennis is begrensd.

A conflict arises when a religious community insists on the absolute truthfulness of all statements recorded in the Bible. This means an intervention on the part of religion into the sphere of science; this is where the struggle of the Church against doctrines of Galileo and Darwin belongs.

My scientific work is motivated by an irresistible longing to understand the secrets of nature and by no other feeling. My love for justice and striving to contribute towards the improvement of human conditions are quite independent from my scientific interests.