The brightest flashes in the world of thought are incomplete until they have been proved to have their counterparts in the world of fact. - John Tyndall

[K]nowledge and progress are the fruits of action.

The logical feebleness of science is not sufficiently borne in mind. It keeps down the weed of superstition, not by logic but by slowly rendering the mental soil unfit for its cultivation.

Then arose the sect of the Gnostics—men who know — who laid claim to the possession of a perfect science, and who, if they were to be believed, had discovered the true formula for what philosophers called 'the Absolute.' But these speculative Gnostics were rejected by the conservative and orthodox Christians of their day as fiercely as their successors the Agnostics —men who don't know—are rejected by the orthodox in our own.