If we inquire into the circumstances that favor and promote this extensive circle of acquisitions, we shall find several that may be named as of importance. In the first place, a natural activity of temperament, or an abundant flow of power to the active mem bers, as shown in a great and various mobility of the frame, is a good basis of bodily acquirements. When the force of the system runs feebly towards the muscular frame Work, being perhaps expended in other ways, as in the thinking powers, mote time is requisite to attain difficult mechanical arts. Another important circumstance is the acuteness or delicacy of the sense involved in the operation. A keen eye, sensitive to minute degrees of effect, is wanted in all the various occupations that turn ou visible appearances; a good ear is indispensable to music and the arts of producing sounds; and so on. With a naturally dull sensibility to flavor, no man can easily become a good cook, or a taster of tea or wine. The third consideration is the natural power of adhesive association belonging to the individual character, Some minds have Originally a more powerful adhesiveness than others, either for things genetally, or for special departments. We see this when a number of boys come together at school, and in apprentices learning together. Some are always found taking the start . of the rest in rapidity of acquire ment; and although the reason may be found iu some of the other circumstances now mentioned, yet observation shows that when everything else is allowed for, there remain natural differences in the rapidity with which the adhesive bond is cemented; some acquiring without effort what others take both time and labor to accomplish. The fourth principal circumstance is the interest taken in the work, or the degree to which it engages the feelings of the learner. This is a material consideration, accounting for the acquisitions made in matters that we have a strong taste for, without our having a pre eminence iu those other points that constitute natural capacity. These four conditionS apply more or less to acquisition generally.
A detailed exemplification of this great principle of our nature might be given through all the departments of the human intellect. The acquirements of speech, as already said, contain a wide range of instances. The adhesion of language is partly in the vocal organs, partly in the ear, and partly in the eye, when we come to written and printed characters. The associations of names with things, with actions (as in obeying directions and command), and with other names (in acquiring foreign languages), are a gradual growth favored by such conditions as the above. The acquirements in science, fine art, and business, and in everything that constitutes skill or knowledge, proceed upon this plastic property of the mind. It also enlarges the sphere of our pleasures and pains. There are connections established in the mind between our states of feeling and the things that have often accompanied them, so that the accompaniment shall have power to revive the feeling. It is thus that we contract affections, both benevolent and malevo lent, towards persons and things, our friends, our home, our country, our property, our pursuits.
This power of stirring up dependent associations to an extent that may be almost called unlimited (although there are limitations), is peculiar to the animal organization. Nothing parallel to it occurs in the mineral or vegetable world. It.is a property of mind alone, and has its seat'in the noiVoUS tistde. We know that growth or change is requisite to the progress of the adhesion; for it proceeds most rapidly in youth, health, and nutrition, and decays in old age, and during exhaustion and disease. And even to keep our acquisitions from fading away, it is requisite that they should be occasionally revived. A language acquired in early years may be utterly lost, by disuse. Sustained practice seems particularly necessary in early education; children's acquisitions are very liable to disintegrate, if not kept up and confirmed by new additions.
Lau of Shnilarity.—This may be expressed as follows: Present actions, sensations, thoughts, and emotions tend to revive their Lth, among precious impressions.
If the mind worked only by the principle of contiguity, nothing would ever occur to us except in some connection already formed. But sonic explanation is necessary as to the precise relationship subsisting between the two distinct forces of mental resuscitation, in order to show at once their distinctness and their connection. When the cohesive link between any two contiguous actions, sensations, or ideas is confirmed by a new occurrence or repetition, it is perfectly obvious that the present impression must revive the sum-total of the past impressions, or reinstate the whole mental condition left on the occasion immediately preceding. Thus, if I am disciplining myself in the act of draw
ing a round figure with my hand, any present effort must recall the state of the muscular and nervous action, or the precise bent acquired at the end of the previous effort, while that effort had to restore the condition at the end of the one preceding, and so on But this reinstatement of a former condition by a present net of the same kind, is really and truly a case of the principle before us, or of like recalling like; and without such recall, the progressive adhesion of contiguous things would be impossible. It would appear, therefor, that similarity is tacitly assumed in the operation of contiguity, and is indis pensable to the process by which our acquisitions are gradually built up. Why, then, do we set up the associating force of likeness as something independent and distinct? To answer this question we must advert to the fact that in those cases where the same impression is deepened by every new repetition, the old and the new arc not merely similar, they are identical, and the resuscitation takes place without fail, and as a matter of course. But in going deeper into the explanation of the human intellect, we encounter many classes of similars, where there is not absolute identity, but the mixing up of a cer tain amount of diversity with the likeness actually existing. The botanist classing together all the plants of the same order, as, for example, the rosueta, has to be struck with the occurrence of certain common characters—viz., the properties that distinguish the order—in the midst of great varieties in all other respects. It is important that he recognize these general marks, whether the plants be trees or shrubs, whether they be poisonous or wholesome, and under many other diversities. It is exceedingly important in science, in the business of life, and even in the creations of fine art, that the mind should take cognizance of likeness surrounded by unlikeness; which is the case that renders it necessary to characterize as distinct the associating force now under discussion. In the case of perfect identity between a present and a past impression, the past is recovered, and fused with the present, instantaneously and surely. So quick and certain is the process, that we lose sight of it altogether; we are scarcely made aware of the existence of an associating link of similarity under such circumstances. But when we pass from perfect to imperfect or partial identity-, we are more readily led to perceive the existence of this link of attraction between similars, for we find that the restoration sometimes does not take place; cases occur where we fail to be struck with a similitude: the spark of resuscitation does not pass between the new impression and the old dormant one. Then it is that we recognize differences between different minds; one man tracing resemblance and making out identity better than another. Moreover, we can assign reasons connected with the culture of the individual, which partially explain superiority or inferiority in this important faculty; just as we have pointed out the conditions favorable to the rapid growth of the adhesive bond of proximity. The failure in rein stating an old impression by virtue of a present one like it, is solely ascribable to the want of perfect identity. When, in some new presentation of an object, the old familiar form is muffled, obscured, distorted, disguised, or in any way altered, it is just a chance if we recognize it; the amount of likeness still remaining will have a tendency to revive the object., while the points of difference or unlikeness will operate against the revival, and tend to restore things of their own kindred. If we hear a musical air that we are accustomed to, the new impression revives the old as a matter of course; but if the air is played with complex harmonies and accompaniments which are strange to us, it is possible that the effect of these additions may be to check our recognition of the melody; the unlike circumstances may repel the reinstatement of the old experience more strongly than the remaining likeness attracts it. If our hold of the essential character of the melody is but feeble, and if we are stunned and confounded by the new accompaniments, there is every probability that we shall not be put upon the old mental track made by the same air; in other words, we shall not identify the performance.