the theory which attempts to explain its phenomena on mechanical principles.

I cannot help taking this opportunity of expressing a wish, that medical writers would be at more pains than they have been at hitherto, to ascertain the various effects which are produced on the memory by disease and old age. These effects are widely diversified in different cases. In some it would seem that the memory is impaired in consequence of a diminution of the power of attention; in others, that the power of recollection is disturbed, in consequence of a derangement of that part of the constitution on which the association of ideas depends. The decay of memory which is the common effect of age, seems to arise from the former of these causes. It is probable, that, as we advance in years, the capacity of attention is weakened by some physical change in the constitution; but it is also reasonable to think, that it loses its vigor partly from the effect which the decay of our sensibility, and the extinction of our passions, have, in diminishing the interest which we feel in the common occurrences of life. That no derangement takes place, in ordinary cases, in that part of the constitution on which the association of ideas depends, appears from the distinct and circumstantial recollection which old men retain of the transactions of their youth.* In some diseases, this part of the constitution is evidently affected. A stroke of the palsy has been known, (while it did not destroy the power of speech,) to render the patient incapable of recollecting the names of the most familiar objects. What is still more remarkable, the name of an object has been known to suggest the idea of it as formerly, although the sight of the object ceased to suggest the name.

In so far as this decay of memory which old age brings

* Swift somewhere expresses his surprise, that old men should remember their anecdotes so distinctly, and should, notwithstanding, have so little memory as to tell the same story twice in the course of the same conversation; and a similar remark is made by Montaigne, in one of his Essays: "Surtout les Vieillards sont dangereux, à qui la souvenance des choses passées demeure, et ont perdu la souvenance de leurs redites."-Liv. i. cap. ix. (Des Menteurs.)

The fact seems to be, that all their old ideas remain in the mind, connected as formerly by the different associating principles; but that the power of attention to new ideas and new occurrences is impaired.

along with it, is a necessary consequence of a physical change in the constitution, or a necessary consequence of a diminution of sensibility, it is the part of a wise man to submit cheerfully to the lot of his nature. But it is not unreasonable to think, that something may be done by our own efforts, to obviate the inconveniences which commonly result from it. If individuals, who, in the early part of life, have weak memories, are sometimes able to remedy this defect, by a greater attention to arrangement in their transactions, and to classification among their ideas, than is necessary to the bulk of mankind, might it not be possible, in the same way, to ward off, at least to a certain degree; the encroachments which time makes on this faculty? The few old men who continue in the active scenes of life to the last moment, it has been often remarked, complain, in general, much less of a want of recollection, than their cotemporaries. This is undoubtedly owing partly to the effect which the pursuits of business must necessarily have, in keeping alive the power of attention. But it is probably owing also to new habits of arrangement, which the mind gradually and insensibly forms, from the experience of its growing infirmities. The apparent revival of memory in old men, after a temporary decline, (which is a case that happens not unfrequently,) seems to favor this supposition.

One old man, I have, myself, had the good fortune to know, who, after a long, an active, and an honorable life, having begun to feel some of the usual effects of advanced years, has been able to find resources in his own sagacity, against most of the inconveniences with which they are commonly attended; and who, by watching his gradual decline with the cool eye of an indifferent observer, and employing his ingenuity to retard its progress, has converted even the infirmities of age into a source of philosophical amusement.

SECTION II.

Of the Varieties of Memory in different Individuals.

Ir is generally supposed, that, of all our faculties, Memory is that which nature has bestowed in the most unequal degrees on different individuals; and it is far from being impossible that this opinion may be well founded. If, however, we consider, that there is scarcely any man who has not memory sufficient to learn the use of language, and to learn to recognise, at the first glance, the appearances of an infinite number of familiar. objects; besides acquiring such an acquaintance with the laws of nature, and the ordinary course of human affairs, as is necessary for directing his conduct in life; we shall be satisfied that the original disparities among men, in this respect, are by no means so immense as they seem to be at first view; and that much is to be ascribed to different habits of attention, and to a difference of selection among the various objects and events. presented to their curiosity.

As the great purpose to which this faculty is subservient, is to enable us to collect, and to retain for the future regulation of our conduct, the results of our past experience; it is evident that the degree of perfection which it attains in the case of different persons, must vary; first, with the facility of making the original acquisition; secondly, with the permanence of the acquisition; and thirdly, with the quickness or readiness with which the individual is able, on particular occasions, to apply it to use. The qualities, therefore, of a good memory are, in the first place, to be susceptible; secondly, to be retentive; and thirdly, to be ready.

It is but rarely that these three qualities are united in the same person. We often, indeed, meet with a memory which is at once susceptible and ready; but I doubt much, if such memories be commonly very retentive: for, susceptibility and readiness are both connected with a facility of associating ideas, according to their more obvious relations; whereas retentiveness, or tenacious

ness of memory, depends principally on what is seldom united with this facility, a disposition to system and to philosophical arrangement. These observations it will be necessary to illustrate more particularly.

I have already remarked, in treating of a different subject, that the bulk of mankind, being but little accustomed to reflect and to generalize, associate their ideas chiefly according to their more obvious relations; those, for example, of resemblance and of analogy; and above all, according to the casual relations arising from contiguity in time and place: whereas, in the mind of a philosopher, ideas are commonly associated according to those relations which are brought to light in consequence of particular efforts of attention; such as the relations of Cause and Effect, or of Premises and Conclusion. This difference in the modes of association of these two classes of men, is the foundation of some very striking diversities between them in respect of intellectual char

acter.

In the first place in consequence of the nature of the relations which connect ideas together in the mind of the philosopher, it must necessarily happen, that when he has occasion to apply to use his acquired knowledge, time and reflection will be requisite to enable him to recollect it. In the case of those on the other hand, who have not been accustomed to scientific pursuits; as their ideas are connected together according to the most obvious relations; when any one idea of a class is presented to the mind, it is immediately followed by the others, which succeed each other spontaneously according to the laws of association. In managing, therefore, the little details of some subaltern employment, in which all that is required is a knowledge of forms, and a disposition to observe them, the want of a systematical genius is an important advantage; because this want renders the mind peculiarly susceptible of habits, and allows the train of its ideas to accommodate itself perfectly to the daily and hourly occurrences of its situation. But if, in this respect, men of no general principles have an advantage over the philosopher, they fall greatly below him. in another point of view; inasmuch as all the informa

tion which they possess, must necessarily be limited by their own proper experience, whereas the philosopher, who is accustomed to refer every thing to general principles, is not only enabled, by means of these, to arrange the facts which experience has taught him, but by reasoning from his principles synthetically, has it often in his power to determine facts a priori, which he has no opportunity of ascertaining by observation.

It follows, farther, from the foregoing principles, that the intellectual defects of the philosopher are of a much more corrigible nature, than those of the mere man of detail. If the former is thrown by accident into a scene of business, more time will perhaps be necessary to qualify him for it, than would be requisite for the generality of mankind; but time and experience will infallibly, sooner or later, familiarize his mind completely with his situation. A capacity for system and for philosophical arrangement, unless it has been carefully cultivated in early life, is an acquisition which can scarcely ever be made afterwards; and, therefore, the defects which I already mentioned, as connected with early and constant habits of business, adopted from imitation, and undirected by theory, may, when once these habits are confirmed, be pronounced to be incurable.

I am also inclined to believe, both from a theoretical view of the subject, and from my own observations as far as they have reached, that if we wish to fix the particulars of our knowledge very permanently in the memory, the most effectual way of doing it, is to refer them to general principles. Ideas which are connected together merely by casual relations, present themselves with readiness to the mind, so long as we are forced by the habits of our situation to apply them to daily use; but when a change of circumstances leads us to vary the objects of our attention, we find our old ideas gradually to escape from the recollection and if it should happen that they escape from it altogether, the only method of recovering them, is by renewing those studies by which they were at first acquired. The case is very different with a man whose ideas, presented to him at first by accident, have been afterwards philosophically