Mr Bailey's fundamental and reiterated objection to Berkeley's theory is, that it requires us to hold that conceptions or past impressions, derived from one sense, (the touch,) are not merely recalled when another sense (the sight) executes its functions, but are themselves absolutely converted into the present intuitions of that other sense. In his own words, (_Review_, p. 69,) the theory is said to require "a transmutation of the conceptions derived from touch into the perceptions of sight." "According to Berkeley, (says he, _Review_, p. 22,) an internal feeling (i.e. a visual sensation) and an external sensation (i.e. a tactual sensation) having been experienced at the same time: the internal feeling, when it afterwards occurs, not only suggests the idea, but, by doing so, suggests the idea, or, if I may use the figure, infuses the perception of its own externality. Berkeley thus attributes to suggestion an effect contrary to its nature, which, as in the case of language, is simply to revive in our conception what has been previously perceived by the sense."
Now, this objection would be altogether insurmountable if it were true, or if it were a part of Berkeley's doctrine, that the sight has no original intuition of space, or of the reciprocal outness of its objects--in other words, of colours out of colours; for it being admitted that the sight has ultimately such a perception, it would be incumbent on the Berkeleian to show how conceptions derived from another sense, or how perceptions belonging to another sense, could be converted into that perception. We agree with Mr Bailey, in thinking that no process of association could effect this conversion; that if we did not originally see colours to be out of each other, and the points of the same colour to be out of each other, we could never so see them; and that his argument, when thus based on the negation of all original visual extension, and on the supposition that the touch is the sole organ of every species of externality, would remain invulnerable.
But, with the admission of the visual intuition of space, the objection vanishes, and the argument is shorn of all its strength. This admission relieves the theory from the necessity of maintaining, that conceptions derived from touch are transmuted into the perceptions of sight. It attributes to the sight all that ever truly belongs to it, namely, the perception of colours out of one another; it provides the visual intuitions with an externality of their own--and the theory never demands that they should acquire any other; and it leaves to these visual intuitions the office of merely suggesting to the mind tactual impressions, with which they have been invariably associated in place. We say, _in place_; and it will be found that there is no contradiction in our saying so, when we shall have shown that it is the touch, and not the sight, which establishes a protensive interval between the organ and the sensations of vision.