_Learning to judge of Distance not inconsistent with this View._--- Nor does it conflict with this view that we learn to judge of the true distance of objects, and are often deceived in regard to it. The _measurement_ of distance, the more or less of it, is of course a matter of experience, a thing to be learned by practice. It does not follow, however, that we may not by the eye directly, and at first, perceive an object to be external, and removed from us, in other words distant, though we may not know at first _how_ distant. The rays of light that come to us from this external object, may give us direct perception of the object as external, as extended, and as occupying apparently a given locality in space more or less remote, while at the same time it may be left to other senses and to experience to determine how great that distance is. _Questions as to Touch._--Passing now from the sense of sight to that of _touch_, we find similar questions discussed among philosophers respecting the precise information afforded by this sense. Does touch give us immediate perception of externality, extension, form, hardness, softness, etc., including the various mechanical properties of bodies? To this sense it has been common to ascribe these faculties of perception. They are so attributed by Reid, Upham, Wayland, and, I believe, by modern writers generally, with the exception of Brown and Hamilton. _Probability of another Source of Information._--It may be questioned, I think, whether, as regards some of these qualities at least, it is not rather the consciousness of resistance to muscular effort, than the sense of touch, properly speaking, that is the informing source. So, for example, as to hardness; the application of an external body lightly to the hand awakens the sense of touch, but conveys no idea of hardness. Let the same object be allowed to rest with gradually increasing weight upon the hand until it becomes painful, and we get the idea of weight, gravitation, but not of the hardness or impenetrability of the object. It is only when our muscular effort to move or penetrate the external body is met and resisted by the same, that we learn the impenetrability of the opposing body.