The science of the future, while agnostic as to the supersensuous, will replace knowledge by belief in the perceptual sphere, and reserve the term knowledge for the conceptual sphere - the region of their own concepts and ideas - of ether, atom, organic corpuscle, and Loading. Loading... vital force - of physical and plasmic mechanics.

The Grammar of Science (2nd edition), Preface to the Second Edition (pp. vii-viii)