Men understand the world in different ways. The main difference lies in this, that some men are more abstract minded, and they naturally think first of unity and of God, of wholeness, of infinity, and other such concepts, while the minds of other men are concrete, and they cogitate about health and desease, profit and loss. They invent gadgets and remedies. They are less interested in knowing anything than in applying whatever knowledge that they may already have to practical problems. They try to make things work and pay, to heal and teach. The first are called dreamers (if worse names are not given to them), the second kind are recognized as practical and useful. History has often proved the shortsightedness of the practical men and vindicated the lazy dreamers. It has also proved that the dreamers are often mistaken. The historian of science deals with both kinds with equal love, for both are needed. Yet he is not willing to subordinate principles to applications, nor to sacrifice the so called dreamers to the engineers, the teachers, or the healers.
- A History of Science, 1952