It is necessary to take notice, that, as each of our senses has its separate class of sensations, so each has its separate class of ideas. We have ideas of Sight, ideas of Touch, ideas of Hearing, ideas of Taste, and ideas of Smell.
1. By Sight, as we have sensations of red, yellow, blue, &c., and of the innumerable modifications of them, so have we ideas of those colours. We can think of those colours in the dark; that is, we have a feeling or consciousness, which is not the same with the sensation, but which we contemplate as a copy of the sensation, an image of it; something more like it, than any thing else can be; something which remains with us, after the sensation is gone, and which, in the train of thought, we can use as its representative.
2. The sensations of Touch, according to the limitation under which they should be understood, are not greatly varied. The gentle feeling, which we derive from the mere contact of an object, when we consider it apart from the feeling of resistance, and apart from the sensation of heat or cold, is not very different, as derived from different objects. The idea of this tactual feeling, therefore, is not vivid, nor susceptible of many modifications. On the other hand, our ideas of heat and cold, the feelings which we call the thought of them, existing when the sensations no longer exist, are among the most distinct of the feelings which we distinguish by the name of ideas.
55 3. I hear the Sound of thunder; and I can think of it after it is gone. This feeling, the representative of the mere sound, this thinking, or having the thought of the sound, this state of consciousness, is the idea. The hearing of the sound is the primary state of consciousness; the idea of the sound is the secondary state of consciousness; which exists only when the first has previously existed.
The number of sounds, of which we can have distinct ideas, as well as distinct sensations, is immense. We can distinguish all animals by their voices. When I hear the horse neigh, I know it is not the voice of the ox. Why? Because I have the idea of the voice of the ox, so distinct, that I know the sensation I have, is different from the sensation of which that is the copy or representative. We can distinguish the sounds of a great number of different musical instruments, by the same process. The men, women, and children, of our intimate acquaintance, we can distinguish, and name, by their voices; that is, we have an idea of the past sensation, which enables us to declare, that the present is the voice of the same person.
4. That the sensations of Taste recur in thought, when the sensation no longer exists, is a point of every man’s experience. This recurring, in thought, of the feeling which we have by the sense, when the feeling by the sense is gone, is the idea of that feeling, the secondary state of consciousness, as we named it above.[18] That we can distinguish a very 56 great number of tastes, and distinguish them accurately, is proof that we have a vast number of distinct ideas of taste; because, for the purpose of making such distinction, we have just seen that there must be a sensation and an idea; the sensation of the present object, and the idea of the sensation of each of the other objects from which we distinguish it. You have tasted port wine, and you have tasted claret; when you taste claret again, you can distinguish it from port wine; that is, you have the idea of the taste of port wine, in conjunction with the sensation of claret. You call it bad claret. Why? Because, along with the present taste, you have the idea of another, which, when it was sensation, was more agreeable than the present sensation.
[18] Discrimination and Retentiveness (the having of Ideas as the produce of Sensations) are different functions, although mutually involved, and, in all likelihood, developed in proportionate degrees in the same organ. We begin by discriminating changes of impression; this process is necessary in order to our having even a sensation; the more delicate the discriminating power, the greater the number of our primary sensations. He that can discriminate twenty shades of yellow has twenty sensations of yellow; the two statements express the same fact. These various sensations being often repeated, acquire at last an ideal persistence; they can be maintained as ideas, without the originals. The function or power of the Intellect whereby they are thus rendered self-subsisting as ideas, is not the same function as discrimination; we call it Memory, Retentiveness, Adhesiveness, Association, and so on. What may be affirmed about it, on the evidence of induction, is, that where discrimination is good, memory or retentiveness is also good. The discriminative eye for colour is accompanied with a good memory for colour; the musical ear is both discriminative and retentive.—B.
5. Since we distinguish smells, as well as tastes, 57 we have the same proof of the number and distinctness of the ideas of this class of sensations. There is none of the numerous smells to which we have been accustomed, which we do not immediately recognise. But for that recognition the idea of the past sensation must be conjoined with the present sensation.
6. Of that class of sensations, which I have called sensations of disorganization, we have also ideas. We are capable of having the thought of them when the sensation is gone; and that thought is the idea. A spark from the candle flew upon my hand: I had the sensation of burning. I at this moment think of that sensation; that is, I have the idea of that sensation; and I can think of it, as different from ten thousand other painful sensations: that is, I have ideas of as many other sensations of this class.
7. The ideas of the sensations which attend the action of the muscles are among the most important of the elements which constitute our being. From these we have the ideas of resistance, of compressibility, of hardness, of softness, of roughness, of smoothness, of solidity, of liquidity, of weight, of levity, of extension, of figure, of magnitude, of whole and of parts, of motion, of rest. It is, indeed, to be observed, that these are all complex ideas, and that other feelings than the mere muscular feeling are concerned in their composition. In almost all the ideas referrible to the muscular feelings, of sufficient importance to have names, the Will is included. The muscular action is the consequent, the Will the antecedent; and the name of the idea, includes both. Thus the idea of resistance is the thought, or idea, of 58 the feelings we have, when we will to contract certain muscles, and feel the contraction impeded.[19] [20]