548 W. JAMES : THE PERCEPTION OF SPACE. (iV.)

only apprehend it at all by having unconsciously summed these up in our head. It is the old idea of our actual knowledge being drawn-out from a pre-existent potentiality, an idea which, whatever worth it may metaphysically possess, does no good in psychology. My own sensationalistic account has derived most aid and comfort from the writings of Hering, A. W. Volkmann, Stumpf, Leconte, and Schon. All these authors allow ample scope to that Experience which Berkeley's genius saw to be a present factor in all our visual acts. But they give Expe- rience some grist to grind, which the soi-disant ' empiristic ' school forgets to do. Stumpf seems to me the most philo- sophical and profound of all these writers. That Hering should have occasionally been fanciful in his assumptions concerning sensations of the third dimension, does not seem to me fatal to the supposition that we have such sensations. In English there is a certain amount of good anti-as- sociationist criticism. The ablest special works are those of Bailey and of Abbott. To the latter author belongs the honour of first in England discussing the question on the basis of the facts of vision, of which, having been mainly discovered in Germany, the English associationist authorities were almost uninformed. Dr. E. Montgomery's papers in Vol. x. of MIND contain many valuable introspective remarks and critical observations ; but with his notion of an unitary objective space known by the specific energy of a specific central organ, and at definite positions within which we locate each particular sensation, I cannot agree.