their

meaning:

suggest nothing else.

but more than this is needed; it is further necessary that they must every word shall suggest nothing else. The requisite that a word shall suggest its meaning is secured by the power of memory the requisite that it shall suggest nothing else is secured by the not less necessary, though purely secured by negative, power of forgetting. The sound of a word may remem- have been heard a thousand times, under circumstances bering, the second which were never exactly alike; the speaker, the words by for

The first

of these is

getting.

before it in the sentence, the words after it, and all other circumstances, have been constantly varied, excepting only the only important circumstance (using the word circumstance with its literal signification), the circumstance of its meaning. In virtue of the law that strong or often-repeated impressions on the consciousness leave residua in the memory, the word itself and its meaning are remembered; in virtue of the law that feeble or seldom-repeated impressions on the consciousness fade altogether away, the varying and unimportant circumstances under which the word has been heard are forgotten. Of all the complex impressions which have been produced on the mind by the word, as it has been heard a thousand times under as many partly dissimilar circumstances, the varying and unlike elements are forgotten, while the constant elements-that is to say, the sound of the word and its meaning-are retained; and the residua of the thousand impressions, having become alike by the loss of their unlike elements, are indistinguishable, and coalesce into one. By this process, the word comes to remain in the memory, separate, detached, suggesting its meaning, and suggesting nothing else. But if the residua of all the thousand impressions did not lose their unlike elements, they would still be distinguishable, and could not coalesce into one. The word would indeed remain in the memory, but not as a single coalesced residuum; it would not be separate and detached from irrelevant objects: it would no doubt suggest its meaning, but it would suggest so much else that it would not serve the purpose which language is meant to serve.1

1 It may be objected to this, that, in learning a foreign language, we habitually remember a word and its meaning after meeting with it only

I will now sum up the whole of the parallel I have Summary. been endeavouring to draw between organic and mental life and growth.

The organism grows by means of new material brought from without in the food. So the mind grows by means of impressions brought from without by the senses. But food could not of itself build up an organism. The organism is built up out of the materials of the food, by the action of the intelligent organizing principle of life. So the impressions received by the mind from the senses could not of themselves form a mind. They are organized into knowledge, and become part of the mental structure by the action of the intelligent principle of mental life.

It is necessary to organic life and growth not only to be constantly acquiring new material, but also to be constantly parting with old material. So it is necessary to mental life and growth to be not only always acquiring and retaining new impressions, but always also forgetting.

Organic growth is due to the excess of material acquired over material parted with. So mental growth is due to the excess of what is remembered over what is forgotten.

In infancy, when the body is growing most rapidly, it is also most rapidly undergoing waste and parting with material. So in childhood, when the mind is acquiring knowledge the most rapidly, it is also forgetting the most.

:

tion of

habits of

the same

The same law of forgetting, and the necessity of for- Formagetting, are true of a different though closely related set of mental phenomena. I mean the process by which action by habits of action are formed. "We learn to do a thing by law. doing it." The process of learning a mechanical art is this that actions are at first performed voluntarily and with conscious attention; but, in virtue of the law of once. But this is an acquired power. Partly through mere habit, partly through voluntary exertion, the student of a language acquires a power of forming the association between a word and its meaning with peculiar facility. I think that children begin to acquire this power while they are learning to speak. But it is not likely that a trace of it exists at the time when language is nothing to the child but sound; and yet every one's knowledge of language has to begin from that point.

Moral

benefit of forgetting.

habit, the oftener they are repeated the easier they become, until at last, in many cases, they cease to need any cooperation of the will or of the conscious attention. They have of course to be voluntarily set going, but when set going they are continued consensually; the stimulus and guide to each successive action of the muscles being sometimes the action next before it, sometimes the sight of the work or the instrument before the workman. Some musicians become able to perform in this way, the stimulus of sense being given either by the sound of the successive notes, or by the sight of the printed music. I have stated this before, but what I wish to point out now is the perfect similarity between this process and the process by which we learn our own language; or, in more general terms, between the process of acquiring motor habits, and the process of acquiring purely mental associations. I have shown that, in order to have the association between words and their meanings in an available form in the mind, the residua of the impressions of all the times we have heard any word must coalesce in the mind into a practically single residuum; and this is done by forgetting the merely accidental circumstances under which we have heard each word. Just so in learning an art. Before it can be consensually performed the memory of each separate time that it has been practised must be lost, and the residua of them all must coalesce into one, which single residuum constitutes the acquired habitual power.

The necessity under which we are of forgetting is good for us in another way. Our life and our duties are in the present, and it would be bad for us were our thoughts to be too much in the past; but this is for the most part forbidden by the law of the certain though slow and gradual fading away of all impressions which are not renewed. It is in virtue of this law that time mitigates grief, even when no nobler cause is at work.1

1 "We forget because we must,

And not because we will."

MATTHEW ARNOLD.

is a case of

It is to be observed that the law of the fading away Forgetting of mental impressions is not an independent primary the laws law. It is a case of that law of habit in virtue of of habit. which all vital tendencies, whether organic or mental, gradually disappear when nothing occurs to call them into exercise.1

1 See the chapter on the Laws of Habit (Chapter XV.).

CHAPTER XXXV.

THE SENSES.

External senses.

That of heat is distinct.

The muscular

sense

belongs to touch.

IN

N the foregoing chapters it has not been necessary to speak of sensations and the consciousness of them further than as general facts: there has been no occasion for discriminating between the various kinds of sensations. But before entering on the consideration of the complex facts of perception, and of our conceptions of time and space, it will be necessary to consider the peculiarities of the various senses, and of the various ways in which they are related to the mind. For the analysis of the more general facts of mind, it is only necessary to take into account the general fact of sensation; but for the analysis of the more special facts of mind, we must also take into account the special facts of the various senses.

It is not necessary in the present chapter to make any further mention of the visceral sensations, such as hunger and thirst, and the sensations of being well or ill. For the present purpose we have to do only with the external senses; that is to say, those senses by means of which we obtain information concerning things external to the sentient organism.

The external senses are usually enumerated as five; namely, touch, taste, smell, sight, and hearing. The sense of heat, however, is really a distinct sense, though it has its seat in the same nerves with the sense of touch. The "muscular sense," or sense of muscular action, is classed by many as a distinct sense; but I shall state my reasons for regarding it as not really separable from the sense of