begins with the act of recognising these pervasive entities, which having character and ideal permanence can furnish common points of reference for different moments of discourse. Save for ideas no perception could have significance, or acquire that indicative force which we call knowledge. For it would refer to nothing to which another perception might also have referred; and so long as perceptions have no common reference, so long as successive moments do not enrich by their contributions the same object of thought, evidently experience, in the pregnant sense of the word, is impossible. No fund of valid ideas, no wisdom, could in that case be acquired by living.
Ideas, although their material is of course sensuous, are not sensations nor perceptions nor objects of any possible immediate experience: they are creatures of intelligence, goals of thought, ideal terms which cogitation and action circle about. As the centre of mass in a body, while it may by chance coincide with one or another of its atoms, is no atom itself and no material constituent of the bulk that obeys its motion, so an idea, the centre of mass of a certain mental system, is no material fragment of that system, but an ideal term of reference and signification by allegiance to which the details of consciousness first become parts of a system and of a thought. An idea is an ideal. It represents a functional relation in the diffuse existences to which it gives a name and
