538 w. JAMES :

achievement of note in the study of space-perception was Berkeley's theory of vision. This undertook to establish two points, first that distance was not a visual, but a tactile form of consciousness, suggested by visual signs; secondly, that there is no one quality or " idea " common to the sensations of touch and sight, such that prior to experi- ence one might possibly anticipate from the look of an object anything about its felt size, shape or position, or from the felt touch of it anything about its look. In other words the primitively chaotic or semi-chaotic condition of our various sense-spaces was established for good by Berkeley ; and he bequeathed to psychology the problem of describing the manner in which the deliverances are harmonised so as all to refer to one and the same ex- tended world. His disciples in Great Britain have solved this problem after Berkeley's own fashion, and to a great extent as we have done ourselves, by the ideas of the various senses sug- gesting each other in consequence of Association. But, either because they were intoxicated with the principle of associa- tion, or because in the number of details they lost their general bearings, they have forgotten, as a rule, to state under what sensible form the primitive spatial experiences are found, which later became associated with so many other sensible signs. Heedless of their master Locke's precept, that the mind can frame unto itself no one new simple idea, they seem for the most part to be trying to explain the extensive quality itself, account for it, and evolve it, by the mere asso- ciation together of feelings which originally possessed it not. They first evaporate the content of extension by making the latter tantamount to mere ' coexistence/ and then explain coexistence as being the same thing as succession, provided it be an extremely rapid or a reversible succession. Space- perception thus emerges without being anywhere postulated. The only things postulated are unextended feelings and time. Says Thomas Brown (Lecture xxiii.) : "I am inclined to reverse exactly the process commonly supposed ; and instead of deriving the measure of time from extension, to derive the knowledge and original measure of extension from time". Brown and both the Mills think that retinal sensations, colours, in their primitive condition, are felt with no exten- sion and that the latter merely becomes inseparably asso- ciated with them. John Mill says: "Whatever may be the retinal impression conveyed by a line which bounds two colours, I see no ground for thinking that by the eye alone we could acquire the conception of what we now