But man is not a mere seeing animal. He has other senses besides: He has, for example, the sense of touch, and one of the most important offices which this sense performs, is to break up the identity or cohesion which subsists between sight and its objects. And how? We answer, by teaching us to associate _vision in general_, or the abstract _condition_ regulating our visual impressions, with the presence of the small tangible body we call the eye, and _vision in particular_, or the individual sensations of vision, (i.e. colours,) with the presence of immeasurably larger bodies revealed to us by touch, and tangibly external to the tangible eye. Sight, as we have said, does not inform us that its sensations are situated in the eye: it does not inform us that we have an eye at all. Neither does touch inform us that our visual sensations are located in the eye. It does not lead us to associate with the eye any of the visual phenomena or operations _in the first instance_. If it did, it would (_firstly_) either be impossible for it _afterwards_ to induce us to associate them with the presence of tangible bodies distant and different from the eye: or, (_secondly_), such an association would merely give birth to the abstract knowledge or conclusion, that these bodies were in one place, while the sensations suggesting them were felt to be associated with something in another place; colour would not be seen--as it is--incarnated with body: or, (_thirdly_), we should be compelled to postulate for the eye, as many philosophers have done, in our opinion, most unwarrantably, "a faculty of projection"[37] by which it might dissolve the association between itself and its sensations, throwing off the latter in the form of colours over the surface of things, and reversing the old Epicurean doctrine that perception is kept up by the transit to the sensorium of the ghosts or _simulacra_ of things,
Quæ, quasi membranæ, summo de corpore rerum, Direptæ, volitant ultro citroque per auras.[38]
It is difficult to say whether the hypothesis of "cast-off films" is more absurd when we make the films come from things to us as spectral effluxes, or go from us to them in the semblance of colours.