In the human economy, the former is often confounded with the latter. By custom we mean a frequent reiteration of the same act; by habit, the effect which custom produces on the mind or body. This curious subject falls to be considered first in a moral, and secondly in a physical light.

1. Influence of Custom and Habit on the Mind. Custom has such influence upon many of our feelings, by warping and varying them, that its operations demand the attention of all those who desire to become acquainted with human nature. The subject, however, is intricate. Some pleasures are fortified by custom; and yet custom begets familiarity, and consequently indifference:

If all the year were playing holidays, To sport would be as tedious as to work; But when they seldom come, they wish'd-for come, And nothing pleaseth but rare accidents.

In many instances, satiety and disgust are the consequences of reiteration. But though custom blunts the edge of distress and of pain, yet the want of any thing to which we have been long habituated is a sort of torture. A clue to guide us through all the intricacies of this labyrinth would be an acceptable present.

Whatever be the cause, it is certain that we are much influenced by custom; it has an effect upon our pleasures, upon our actions, and even upon our thoughts and sentiments. Habit makes but little figure during the vivacity of youth; in middle age it gains ground; and in old age it governs without control. At that period of life, generally speaking, we eat at a certain hour, take exercise at a certain hour, go to rest at a certain hour, all by the direction of habit; nay, a particular seat, table, or bed, comes to be essential; and a habit in any of these cannot be controlled without uneasiness.

Any slight or moderate pleasure, frequently reiterated for a long time, forms a peculiar connection between us and the thing which causes the pleasure. This connection, termed habit, has the effect of awakening our desire or appetite for that thing when it returns not as usual. During the course of enjoyment, the pleasure rises insensibly higher and higher till a habit becomes established, at which time the pleasure is at its height. It continues not, however, stationary; the same customary reiteration which carried it to its height, brings it down again by insensible degrees, even lower than it was at first.

To introduce an active habit, frequency of acts is not sufficient without length of time. The quickest succession of acts in a short time is not sufficient, nor a slow succession in the longest time. The effect must be produced by a moderate gentle action, and a long series of easy touches, removed from each other by short intervals. Nor are these sufficient without regularity in the time, place, and other circumstances of the action; for the more uniform any operation is, the sooner it becomes habitual. And this holds equally in a passive habit; variety, in any remarkable degree, preventing the effect. Thus any particular food will scarcely ever become habitual where the manner of dressing it is varied. The circumstances requisite, then, to augment a moderate pleasure, and at the long-run to form a habit, are weak uniform acts, reiterated during a long tract of time, without any considerable interruption; and every agreeable cause which operates in this manner will grow habitual.

Affection and aversion, as distinguished from passion on the one hand, and from original disposition on the other, are in reality habits respecting particular objects, acquired in the manner above stated. The pleasure of social intercourse with any person must originally be faint, and frequently reiterated, in order to establish the habit of affection. Affection thus generated, whether it be friendship or love, seldom swells into any tumultuous or vigorous passion; but it is nevertheless the strongest cement that can bind together two individuals of the human species. In like manner, a slight degree of disgust often reiterated with regularity, grows into the habit of aversion, which commonly subsists for life.

Objects of taste which are delicious, so far from tending to become habitual, are apt by indulgence to produce satiety and disgust. No man contracts a habit of using sugar, honey, or sweetmeats, as he does tobacco.

These violent delights have violent ends, And in their triumphs die. The sweetest honey Is loathsome in its own deliciousness, And in the taste confounds the appetite: Therefore love moderately, long love doth so; Too swift arrives as tardy as too slow.

The same observation holds with respect to all such objects as, being extremely agreeable, raise violent passions, which are incompatible with a habit of any kind, and, in particular, never produce affection nor aversion.

It is perhaps not easy to say why moderate pleasures gather strength by custom; but two causes concur to prevent that effect in the more intense pleasures. These, by an original law in our nature, increase quickly to their full growth, and decay with no less precipitation; while custom is too slow in its operation to overcome the force of this law. The other cause is not less powerful. Exquisite pleasure is extremely fatiguing, occasioning, as a naturalist would say, great expense of animal spirits; and of this the mind cannot bear so frequent gratification as to superinduce a habit. If the thing which raises the pleasure return before the mind has recovered its tone and relish, disgust ensues instead of pleasure.

A habit never fails to diminish us of the wonted time of gratification, by raising a feeling for want of the object, and a desire to have it. The sensation of want is always first felt; the desire naturally follows; and upon presenting the object, both vanish instantaneously. Thus a man accustomed to tobacco feels at the end of the usual interval a confused sensation of want, which at first points to nothing in particular, though it soon settles upon its accustomed object. And the same may be observed in persons addicted to drinking, who are often in an uneasy and restless state before they think of the bottle. In pleasures indulged regularly, and at equal intervals, the appetite, remarkably obsequious to custom, returns regularly with the usual time of gratification; but not sooner, even though the object be presented. This sensation of want arising from habit seems directly opposite to that of satiety; and it must appear singular, that frequency of gratification should produce effects so opposite as the feelings of excess and of want.

The appetites which respect the preservation and propagation of our species are attended with pain, arising from a want similar to that occasioned by habit. Hunger and thirst are uneasy sensations of want, which always precede the desire of eating and drinking; and a pain for want of carnal enjoyment precedes the desire of an object. The sensation being thus felt independently of an object, cannot be cured but by gratification. Very different is an ordinary passion, in which desire precedes the sensation of want. Such a passion cannot exist except while the object is in view; and therefore, by removing the object out of thought, it vanishes with the desire and sensation of want.

The natural appetites above mentioned differ from habit in this, that they have an undeterminate direction toward all objects of gratification in general; whereas an habitual appetite is directed to a particular object. The attachment we feel by habit towards a particular woman differs widely from the natural passion which comprehends the whole sex; and the habitual relish for a particular dish is far from being the same with a vague appetite for food. But notwithstanding this difference, it is still remarkable that nature has enforced the gratification of certain natural appetites essential to the species, by a pain of the same sort with that which habit produces.

The pain of habit is less under our power than any other sensation arising from want of gratification. Hunger and thirst are more easily endured, especially at first, than an unusual intermission of any habitual pleasure; and persons are often heard to declare they would forego sleep or food rather than tobacco. We must not however conclude, that the gratification of an habitual appetite affords the same delight with the gratification of one which is natural. Far from it; the sensation of want only is greater.

The causes of the emotions hitherto considered are either an individual, such as a companion, a certain dwelling-place, a certain amusement, or a particular species, Custom such as coffee, mutton, or any other food. But habit is not confined to such. A constant train of trifling diversions may form such a habit in the mind that it cannot be easy a moment without amusement. A variety in the objects prevents a habit as to any one in particular; but as the train is uniform with respect to amusement, the habit is formed accordingly; and that sort of habit may be denominated a generic habit, in opposition to the former, which is a specific habit. The habit of a town life, of country sports, of solitude, of reading, or of business, where sufficiently varied, are instances of generic habits. Every specific habit has a mixture of the generic; for the habit of any one sort of food makes the taste agreeable, and we are fond of that taste wherever it is found. Thus a man deprived of an habitual object, attaches himself to that which most resembles it. Deprived of tobacco, any bitter herb will do rather than submit to want. A habit of punch makes wine a good resource. Accustomed to the sweet society and comforts of matrimony, the man unhappily deprived of his beloved object inclines the sooner to take to himself a second. And in general, when we are deprived of an habitual object, we are fond of its qualities in any other object.

The reasons above assigned show why the causes of intense pleasure become not readily habitual; but now we discover that these reasons conclude only against specific habits. In the case of a weak pleasure, a habit is formed by frequency and uniformity of reiteration, which, in the case of an intense pleasure, produces satiety and disgust. But it is remarkable, that satiety and disgust have no effect, except as to that which occasions them. A surfeit of honey produces not a loathing of sugar; and intemperance with one woman creates no disrelish of the same pleasure with others. Hence it is easy to account for a generic habit in any intense pleasure; the delight we had in the gratification of the appetite inflames the imagination, and induces us to search with avidity for the same gratification in whatever other object it can be found. And thus uniform frequency in gratifying the same passion upon different objects, produces at length a generic habit. In this manner one acquires an habitual delight in high and poignant sauces, rich dresses, fine equipages, crowds of company, and in whatever is commonly termed pleasure. There concurs, at the same time, to introduce this habit, a peculiarity observed above, that reiteration of acts enlarges the capacity of the mind to admit a fuller gratification than originally, with regard to frequency as well as quantity.

Hence it appears, that though a specific habit cannot be formed except upon a moderate pleasure, a generic habit may be formed upon any sort of pleasure, moderate or immoderate, that has variety of objects. The only difference is, that a weak pleasure runs naturally into a specific habit, whereas an intense pleasure is altogether averse to such a habit. In a word, it is only in singular cases that a moderate pleasure produces a generic habit; but an intense pleasure cannot produce any other habit.

The appetites which respect the preservation and propagation of the species are formed into a habit in a peculiar manner; the time as well as measure of their gratification being much under the power of custom, which, introducing a change upon the body, occasions a proportional change in the appetites. Thus, if the body be gradually formed to a certain quantity of food at stated times, the appetite is regulated accordingly; and the appetite is again changed when a different habit of body is introduced by a different practice. Here it would seem that the change is not made upon the mind, which is commonly the case in passive habits, but upon the body alone. When rich food is brought down by ingredients of a plainer quality, the composition is susceptible of a specific habit. Thus the sweet taste of sugar, rendered less poignant in a mixture, may in course of time produce a specific habit for such mixture. As moderate pleasures, by becoming more intense, tend to generic habits; so intense pleasures, by becoming more moderate, tend to specific habits.

The beauty of the human figure, by a special recommendation of nature, appears to us supreme amidst the great variety of beauteous forms bestowed upon animals. The various degrees in which individuals enjoy that property, render it an object sometimes of a moderate, sometimes of an intense passion. The moderate passion, admitting frequent reiteration without diminution, and occupying the mind without exhausting it, grows gradually stronger till it become a habit. Nay, instances are not wanting of a face at first disagreeable being afterwards rendered indifferent by familiarity, and at length agreeable by custom. On the other hand, consummate beauty, at the very first glance, fills the mind so as to admit of no increase. Enjoyment lessens the pleasure; and if often repeated, it commonly ends in satiety and disgust. The impressions made by consummate beauty, in a gradual succession from lively to faint, constitute a series opposite to that of faint impressions waxing gradually more and more lively, until they produce a specific habit. But the mind, when accustomed to beauty, contracts a relish for it in general, though often repelled from particular objects by the pain of satiety; and thus a generic habit is formed, of which inconstancy in love is the necessary consequence; for a generic habit, comprehending every beautiful object, is an invincible obstruction to a specific habit, which is confined to one.

One effect of custom, different from any that has yet been explained, must not be omitted, because it makes a great figure in human nature. Though custom augments moderate pleasures, and lessens those that are intense, it has a different effect with respect to pain; for it blunts the edge of every sort of pain and distress, whether faint or acute. Uninterrupted misery, therefore, is attended with one good effect, that if its torments be incessant, custom hardens us to bear them.

The changes produced in forming habits are curious. Moderate pleasures are augmented gradually by reiteration, until they become habitual, and then they are at their height; but they are not long stationary; for from that point they gradually decay, until they vanish altogether. The pain occasioned by want of gratification runs a different course; it increases uniformly, and at last becomes extreme, when the pleasure of gratification is reduced to nothing.

The effect of custom with relation to a specific habit is displayed throughout all its varieties in the use of tobacco. The taste of that plant is at first extremely unpleasant; but our disgust lessens gradually until it vanish altogether, at which period the taste is neither agreeable nor disagreeable. Continuing the use of the plant, however, we at length begin to relish it; and our relish improves by use, till it arrive at perfection. From that period it gradually decays, while the habit is in a state of increase, and consequently the pain of want. The result is, that when the habit has acquired its greatest vigour, the relish is gone; and accordingly we often smoke and take snuff habitually, without so much as being conscious of the operation. We must expect gratification after the pain of want, the pleasure of which gratification is the greatest when the habit is the most vigorous. It is of the same kind with the pleasure which one feels upon being delivered from the rack. This pleasure, however, is but occasionally the effect of habit, and, however exquisite, is avoided as much as possible, because of the pain which precedes it.

With regard to the pain of want, we can discover no difference between a generic and a specific habit; but these habits differ widely with respect to the positive pleasure. We have had occasion to observe, that the pleasure of a specific habit decays gradually until it becomes imperceptible; but the pleasure of a generic habit, on the contrary, being supported by variety of gratification, suffers little or no decay after it has arrived at its height. However it may be with other generic habits, the observation certainly holds good with respect to the pleasures of virtue and knowledge. The pleasure of doing good has an unbounded scope, and may be so variously gratified that it can never decay. Science is equally unlimited; our appetite for knowledge having an ample range of gratification where discoveries are recommended by novelty, by variety, by utility, or by all of these together.

In this intricate inquiry we have endeavoured, but without success, to discover by what particular means it is that custom influences us; and now nothing remains but to hold our nature to be so framed as to be susceptible of such influence. And supposing it purposely so framed, it will not be difficult to detect several important final causes. That the power of custom is a happy contrivance for our good, cannot have escaped any one who reflects that business is our province, and pleasure our relaxation only. But satiety is necessary to check excessive pleasures, which otherwise would engross the mind, and disqualify us for business. On the other hand, as business is sometimes painful, and is never pleasant beyond moderation, the habitual increase of moderate pleasure, and the conversion of pain into pleasure, are admirably contrived for disappointing the malice of fortune, and for reconciling us to whatever course of life it may be our lot to pursue.

How use doth breed a habit in a man! This shadowy desert, unfrequented woods, I better brook than flourishing peopled towns. Here I can sit alone, unseen of any, And to the nightingale's complaining notes Tune my distresses, and record my woes.

As the foregoing distinctions between intense and moderate habits hold only in pleasure, every degree of pain being softened by time, custom is a catholic remedy for pain and distress of every kind; and of this ordination the final cause requires no illustration.

Another final cause of custom has in a great measure been overlooked; namely, that it has a greater influence than any other known cause in putting the rich and the poor upon a level; for weak pleasures, the share of the latter, become fortunately stronger by custom, whilst voluptuous pleasures, the share of the former, are continually losing ground by satiety. Men of fortune, who possess palaces, sumptuous gardens, and rich fields, enjoy them less than passengers do. The goods of fortune are not unequally distributed, the opulent often possessing what others enjoy.

And indeed, if it be the effect of habit to produce the sensation of want in a high degree while there is little pleasure in enjoyment, a voluptuous life is of all the least to be envied. Those who are habituated to high feeding, easy vehicles, rich furniture, a crowd of valets, with much deference and flattery, enjoy but a small share of happiness whilst they are exposed to manifold distresses. To a man enslaved by ease and luxury, even the petty inconveniences of travelling, as a rough road, bad weather, or homely fare are serious evils; he loses his tone of mind, turns peevish and would wreak his resentment even upon the common accidents of life. Better far to use the goods of fortune with moderation. A man who by temperance and activity has acquired a hardy constitution, is guarded against ex ternal accidents on the one hand, and on the other is provided with great variety of enjoyment, which he has ever at command.

II. Effects of Custom and Habit in the Animal Economy. These may be reduced to four heads, first, on the simple solids; secondly, on the organs of sense; thirdly, on the moving power; fourthly, on the whole nervous system.

Effects on the Simple Solids. Custom determines the degree of flexibility of which they are capable. By frequently repeated flexion, the several particles of which these solids consist are rendered more supple and moveable on each other. A piece of catgut, for instance, when on the stretch, and having a weight appended to its middle, will thereby be bended perhaps half an inch; and afterwards, by frequent repetitions of the same weight, or by increasing the weight, the flexibility will be rendered double. The degree of flexibility has a great effect in determining the degree of oscillation, provided that elasticity is not affected; but if it go beyond this, it produces flaccidity. Again, custom determines the degree of tension; for the same elastic chord that now oscillates in a certain degree of tension, will, by frequent repetition of these oscillations, be so far relaxed, that the extension must be renewed in order to produce the same tension, and consequently the same vibrations, as at first. This appears in many instances in the animal economy, as when different muscles concur to give a fixed point or tension to each other. Thus a weakly child totters as it walks along; but by giving it a weight to carry, and by thus increasing the tension of the system, it proceeds more steadily. In like manner, the fulness of the system gives strength, by distending the vessels everywhere, and so giving tension; and hence a man, by good nourishment, from being weak, acquires a great increase of strength in a few days; whilst, on the other hand, evacuations weaken by taking off the tension.

Effects on the Organs of Sense. Repetition gives a greater degree of sensibility, in as far only as it renders perception more accurate. Repetition alone produces lasting impressions, and thus lays the foundation of memory; for single impressions are retained but for a short time, and are soon forgotten. Thus, a person who at present has little knowledge of cloths, will, by frequent handling them, acquire a skill of discerning them which to others seems almost impossible. Many are apt to mistake this for a nicer sensibility, but they are much mistaken; for it is an universal law, that the repetition of impressions renders us less acute. This is well illustrated by the operation of medicines; for all medicines which act on the organs of sense must, after some time, be increased in their dose to produce the same effects as at first. This affords a rule in practice with regard to these medicines; for after a certain time it becomes necessary to change one medicine even for a weaker of the same nature. Thus medicines which have no great apparent force separately, are found, by long use, to destroy the sensibility of the system to other impressions. But to this general rule, that, by repetition, the force of impressions is more and more diminished, there are some exceptions. Thus persons, by a strong emetic, have had their stomachs rendered so irritable that one twentieth of the first dose was sufficient to produce the same effect. This, however, chiefly takes place when the emetic is repeated every day; for if the same dose be given at pretty considerable intervals, the general rule is observed to hold good. Thus two contrary effects of habit are to be noted; and it is proper to observe, that the greater irritability is more readily produced when the first impression is great, as in the case above given of the strong emetic. This may be further illustrated by the effect of fear, which is commonly observed to be diminished on repetition,—an effect which can only be attributed to custom; whilst, on the other hand, there are instances of persons who, having once been greatly frightened, have ever afterwards continued slaves to fears excited by impressions of the like kind, however slight; a consequence which must be imputed entirely to excess of the first impression, as has been already observed. To this head also belongs the association of ideas, which is the foundation of memory and of all our intellectual faculties, and is principally the effect of custom. With regard to the body also, these associations often take place. And sometimes, in producing effects on the body, associations seemingly opposite are formed, which, through custom, become absolutely necessary; for instance, a person long accustomed to sleep in the neighbourhood of a great noise, is so far from being incommodeed on that account, that such noise becomes afterwards necessary in order to produce sleep. It will be of use to attend to this in medical practice; for, however opposite it may seem at the time, we ought to allow for whatever has usually attended the purpose we design to effect. Thus, in the instance of sleep, we must not exclude noise when we want to procure rest, or any cause which may seem opposite to such an effect, provided custom has rendered it necessary.

Effects on the Moving Fibres. A certain degree of tension is necessary to motion, which is to be determined by custom; for instance, a fencer, accustomed to a particular foil, cannot have the same steadiness or activity with one heavier or lighter. It is necessary also that every motion should be performed in the same situation or posture of the body as the person has been accustomed to employ in that motion. Thus, in any chirurgical operation, a certain posture is recommended; but if the operator has been accustomed to another, such an one, however awkward, becomes necessary afterwards to his right performance of the particular operation.

Custom also determines the degree of oscillation of which the moving fibres are capable. A person accustomed to strong muscular exertions is quite incapable of the more delicate movements. Thus writing is performed by small muscular contractions; but if a person has been accustomed to stronger motions with these muscles, he will write with much less steadiness.

This subject of tension, formerly attributed to the simple fibres, is probably more strictly applicable to the moving ones: for besides a tension from flexion, there is also a tension from irritation and sympathy; as, for instance, the tension of the stomach from food, which gives tension to the whole body. Wine and spirituous liquors give tension; and, in like manner, a person who is so affected with tremor as scarcely to be able to hold a glass of any of these liquors to his lips, has no sooner swallowed it than his whole body becomes steady; and after the system has been accustomed to such stimuli, if they are not applied at the usual times, the whole body becomes flaccid, and consequently unsteady in its motions.

Again, custom gives facility of motion. This seems to proceed from the distention which the nervous power gives to the moving fibres themselves. But in whatever manner it is occasioned, the effect is obvious; for any new or unusual motion is performed with great difficulty.

It is supposed that sensation depends on a communication with the sensorium commune, by means of organs sufficiently distended with nervous influence. We have found that sensibility is diminished by repetition; and we have now to observe, that in some cases it may be increased by repetition, owing to the nervous power itself flowing more easily into the part on account of custom. Attention to a particular object may also determine a greater influx into any particular part, and thus the sensibility and irritability of that particular part may be increased. But with regard to facility of motion, the nervous power, no doubt, flows most easily into those parts to which it has been accustomed; yet facility of motion does not entirely depend on this, but in part also on the concurrence of the action of a great many muscles. Accordingly, Winslow has observed, that in performing any motion, a number of muscles concur to give a fixed point to those intended chiefly to act, as well as to others designed to vary and modify their action. This, however, is assisted by repetition and the freer influx; as by experience we know the proper attitude for giving a fixed point in order to perform any action with facility and steadiness.

Custom gives a spontaneous motion also, which seems to recur at stated periods, even when the exciting causes are removed. Thus, if the stomach has been accustomed to vomit from a particular medicine, it will require a much smaller dose than at first, nay, even the very sight or remembrance of it will be sufficient to produce the effect; and there are not wanting instances of habitual vomiting, from the injudicious administration of emetics. It is on this account that all spasmodic affections so easily become habitual, and are so difficult of cure; for we must not only avoid all the exciting causes, even in the smallest degree, but also their associations.

Custom also gives strength of motion; and strength depends on strong oscillations, a free and copious influx of the nervous power, and on dense solids. But in what manner all these circumstances are brought about by repetition, has been already explained. The effect of custom in producing strength may be thus illustrated: a man who begins with lifting a calf, by continuing the same practice every day, will probably be able to lift it when grown to the full size of a bull.

All this is of considerable importance in the practice of physic, though but too little regarded; for the recovery of weak people in a great measure depends on the use of exercise suited to their strength, or rather below it, frequently repeated and gradually increased. Further, it is necessary to observe, that custom regulates the particular celerity with which each motion is performed, for a person accustomed for a considerable time to one degree of celerity, becomes incapable of a greater: thus, for instance, a man accustomed to slow walking will be out of breath before he can run twenty paces. The train or order in which our motions are performed is also established by custom; for if a man has repeated motions for a certain time in any particular order, he cannot afterwards perform them in any other. Custom also very frequently associates motions and sensations; thus, if a person has been in the use of associating certain ideas with the ordinary stimulus which in health excites urine, without these ideas the usual inclination will scarcely excite that excretion, and, when they occur, will require it even in the absence of the primary exciting cause. It is very common for a person to make urine when going to bed, and if he has been for any length of time accustomed to do so, he will ever afterwards make urine at that time, though otherwise he would often have had no such inclination. By this means some secretions become in a manner subject to the will. The same may be said of going to stool. And this affords us a good rule in the case of costiveness; for by endeavouring to fix a stated time for this evacuation, it will afterwards at such a time more readily return. It is further remarkable, that motions are inseparably associated with other motions. This perhaps very often proceeds from the necessary degree of tension, but it also often depends merely on custom, an instance of which we have in the uniform motions of our eyes.

Effects on the whole Nervous System. We have found that, by custom, the nervous influence may be determined more easily into one part than another; and therefore, as all the parts of the system are strongly connected, the sensibility, irritability, and strength of any particular part may be thus increased. Custom has also the power of altering the natural temperament, and of inducing a new one. It is likewise in the power of custom to render motions periodical, and periodically spontaneous. An instance of this we have in sleep, which is commonly said to be owing to the nervous power being exhausted, the necessary consequence of which is sleep; but if this were the case, the return of sleep should be at different times, according as the causes which diminish the nervous influence operate more or less powerfully; whereas the case is quite otherwise, these returns of sleep being quite regular. This is no less remarkable in the appetites, which return at particular periods, independently of every cause but custom.

There are many other instances of this disposition of the nervous influence to periodical motions, as the story of the idiot of Stafford, recorded by Dr Plot in the Spectator (No. 447), who, being accustomed to tell the hours of the church clock as it struck, told them as exactly when it did not strike by its being out of order. Montaigne tells us of some oxen that were employed in a machine for drawing water, who, after making three hundred turns, which was the usual number, could be stimulated by no whip or goad to proceed farther.

CUSTOMS, or the duties, toll, tribute, or tariff, payable upon merchandise exported and imported. See Excise and Taxation.