We must keep our freedom of mind, ... and must believe that in nature what is absurd, according to our theories, is not always impossible.

Effects vary with the conditions which bring them to pass, but laws do not vary. Physiological and pathological states are ruled by the same forces; they differ only because of the special conditions under which the vital laws manifest themselves.

We must keep our freedom of mind, ... and must believe that in nature what is absurd, according to our theories, is not always impossible.

The investigator should have a robust faith - and yet not believe.

We achieve more than we know. We know more than we understand. We understand more than we can explain.

The joy of discovery is certainly the liveliest that the mind of man can ever feel.

Man can learn nothing unless he proceeds from the known to the unknown.