A fact in itself is nothing. It is valuable only for the idea attached to it, or for the proof which it furnishes.

Theories are like a stairway; by climbing, science widens its horizon more and more, because theories embody and necessarily include proportionately more facts as they advance.

Those who do not know the torment of the unknown cannot have the joy of discovery.

But while I accept specialization in the practice, I reject it utterly in the theory of science.

Science does not permit exceptions.

As soon as the circumstances of an experiment are well known, we stop gathering statistics. ... The effect will occur always without exception, because the cause of the phenomena is accurately defined. Only when a phenomenon includes conditions as yet undefined,Only when a phenomenon includes conditions as yet undefined, can we compile statistics. ... we must learn therefore that we compile statistics only when we cannot possibly help it; for in my opinion, statistics can never yield scientific truth.

In every enterprise ... the mind is always reasoning, and, even when we seem to act without a motive, an instinctive logic still directs the mind. Only we are not aware of it, because we begin by reasoning before we know or say that we are reasoning, just as we begin by speaking before we observe that we are speaking, and just as we begin by seeing and hearing before we know what we see or what we hear.