Paragraph I. We, as well as the ancients, speak of the five senses, and of a sense, or common sense, which is the abstraction of them. The term 'sense' is also used metaphorically, both in ancient and modern philosophy, to express the operations of the mind which are immediate or intuitive. Of the five senses, two--the sight and the hearing--are of a more subtle and complex nature, while two others--the smell and the taste--seem to be only more refined varieties of touch. All of them are passive, and by this are distinguished from the active faculty of speech: they receive impressions, but do not produce them, except in so far as they are objects of sense themselves. Physiology speaks to us of the wonderful apparatus of nerves, muscles, tissues, by which the senses are enabled to fulfil their functions. It traces the connexion, though imperfectly, of the bodily organs with the operations of the mind. Of these latter, it seems rather to know the conditions than the causes. It can prove to us that without the brain we cannot think, and that without the eye we cannot see: and yet there is far more in thinking and seeing than is given by the brain and the eye. It observes the 'concomitant variations' of body and mind. Psychology, on the other hand, treats of the same subject regarded from another point of view. It speaks of the relation of the senses to one another; it shows how they meet the mind; it analyzes the transition from sense to thought. The one describes their nature as apparent to the outward eye; by the other they are regarded only as the instruments of the mind. It is in this latter point of view that we propose to consider them. The simplest sensation involves an unconscious or nascent operation of the mind; it implies objects of sense, and objects of sense have differences of form, number, colour. But the conception of an object without us, or the power of discriminating numbers, forms, colours, is not given by the sense, but by the mind. A mere sensation does not attain to distinctness: it is a confused impression, sugkechumenon ti, as Plato says (Republic), until number introduces light and order into the confusion. At what point confusion becomes distinctness is a question of degree which cannot be precisely determined. The distant object, the undefined notion, come out into relief as we approach them or attend to them. Or we may assist the analysis by attempting to imagine the world first dawning upon the eye of the infant or of a person newly restored to sight. Yet even with them the mind as well as the eye opens or enlarges. For all three are inseparably bound together--the object would be nowhere and nothing, if not perceived by the sense, and the sense would have no power of distinguishing without the mind.