PRELUDE TO CHAPTER II.
This chapter opens with a continuation of the discussion upon the senses, and, assuming sensation to be an ultimate fact, it argues that vision (taken as an example), must be the office of the eye, or some other sense; if the office of some other sense, then it, unlike every other, will have had assigned to it two different modes of impression. Add to this, that like the visual sense, which perceives colour only, it must be imbued with colour, and this would interfere with its own peculiar office. The further objection to another than its own sense for vision, in its requiring an infinite series of perceptions, is neither clear nor apposite; for, had a sense been made perceptive of double impressions, that faculty would be, as much as a single sense, an ultimate fact. The passage has been a fruitful topic for commentators, as might be supposed, but it still remains the subject of conjecture.