Fantasie is belangrijker dan kennis, want kennis is begrensd.

It is open to every man to choose the direction of his striving; and also every man may draw comfort from Lessing's fine saying, that the search for truth is more precious than its possession.

External conditions can, to a certain extent, reduce, but never cancel individual repsonsibility.

This crippling of individuals I consider the worst evil of capitalism. Our whole educational system suffers from this evil. An exaggerated competitive attitude is inculcated into the student, who is trained to worship acquisitive success as a preparation for his future.

The work on satisfactory formulation of technical patents was a true blessing for me. It compelled me to be many-sided in thought, and also offered important stimulation for thought about physics. Following a practical profession is a blessing for people of my type. Because the academic career puts a young person in a sort of compulsory situation to produce scientific papers in impressive quantity, a temptation to superficiality arises that only strong characters are able to resist.

Those instrumental goods which should serve to maintain the life and health of all human beings should be produced by the least possible labour of all.

In art, and in the higher ranges of science, there is a feeling of harmony which underlies all endeavor. There is no true greatness in art or science without that sense of harmony.