Certain states of our bodily organs are directly followed by certain states or affections of our mind;--certain states or affections of our mind are directly followed by certain states of our bodily organs. The nerve of sight, for example, is affected in a certain manner; vision, which is an affection or state of the mind, is its consequence. I will to move my hand; the hand obeys my will, so rapidly, that the motion, though truly subsequent, seems almost to accompany my volition, rather than to follow it. In conformity with the definitions before given of power and susceptibility, the one as implying a reference to something consequent, the other a reference to something antecedent, I should be inclined to consider the sensation which follows the presence of an external object as indicating a mental susceptibility of being so affected;--the production of muscular motion by the will, as indicating a mental power. But the terms are of less consequence, if you understand fully the distinction that is implied in them; and you may be allowed still, in compliance with the general language, to speak of the power or faculty of sensation or perception, if you mean nothing more, as often as you use these terms, than that the mind is affected in a certain manner, and, therefore, must have had a previous susceptibility of being thus affected whenever certain changes have previously taken place, in that nervous system, with which it is connected. In considering the susceptibilities of the mind, I comprehend, under its _external_ affections, all those phenomena or states of the mind, which are commonly termed _sensations_; together with all our internal organic feelings of pleasure or pain, that arise from states of the nervous system, as much as our other sensations. Many of these are commonly ranked under another head, that of _appetites_,--such as hunger, thirst, the desire of repose, or of change of muscular position, which arises from long-continued exertion; the oppressive anxiety, which arises from impeded respiration, and various other diseases, arising from bodily uneasiness. But these appetites evidently admit of being analysed into two distinct elements,--a pain of a peculiar species, and a subsequent desire of that which is to relieve the pain,--states of mind, of which one may immediately succeed the other; but which are, unquestionably, as different in themselves, as if no such succession took place,--as different as the pleasure of music is from the mere desire of enjoying it again, or as the pain of excessive heat, in burning, from the subsequent desire of coolness. The pain, which is _one_ element of the appetite, is an _external_ affection of the mind, to be classed with our other sensations,--the succeeding desire, which is another element of it, is an _internal_ affection of the mind, to be classed with our other emotions of desire. We might have felt the same pain of hunger, though we had not been