109. Ideas of recollection differ from those of the imagination, principally, in the readiness and strength of the associa tions ; but partly, and in many cases al most entirely, by the connection of the former with known and allowed facts, by various methods of reasoning appropriate to the peculiar circumstances of the case, and by recollecting that we had before considered them as recollections, &c. Great difficulty, however, often exists, especially in the minds of persons with vigorous conceptions, who have not been habitually careful to cultivate accuracy of perceptions, and in the relation of recol lections, to know whether the trains of Ideas presented by the associative power are to be referred to the memory or to the imagination. Such persons, seizing Only the outline of a fact or series of oc currences, from habitual inattention to their sensations, are, from readiness of association, able to fill up the transcript, so as to make it appear plausible to them selves ; and by once or twice detailing it Nvithout minute regard to accuracy, ex cept in those leading features, they give a vigour to the ideas and closeness to the association of them, which leads at last to the full conviction, that the whole is re collected. Cases of this sort are very fre quent ; and they often leave upon the minds of others the belief, that such per sons intentionally depart from truth, whereas sometimes the fact is, that part of their error arises from a desire to give the whole truth, when they have only the materials for a portion of it in their minds. However, the fault is one which should be carefully guarded against ; par ticularly in the early part of life, by mak ing young people of lively imaginations habitually attentive to the minute as well as the leading parts of their impres sions.—All persons are at one time or other at a loss to know whether trains of vivid ideas, succeeding each other readily and rapidly, are ideas of recollection or of imagination, that is, mere reveries : and the more they agitate the matter in their minds, the more does the reverie appear like a recollection. Persons of irritable nervous systems are more sub ject to such fallacies than others ; and insane persons often impose upon them selves in this way, viz. by the vividness of their ideas and associations, produc ed by bodily causes. The same things often happen in dreams.
110. The vividness and readiness of recollected trains, is also one grand means of ascertaining the dates of facts ; for as this diminishes, (other things be ing equal), in proportion to the period which has elapsed since the reception of the ideas, and the formation of the asso ciations, if the vigour of thesebe diminish ed,we refer them to a more remote period, in proportion to that diminution ; and if by any cause it be kept up, the distance of time appears diminished. Thus it is, that if any interesting event, the death of a friend, for instance, have been often recollected and related, till we come to make oral or mental calculations, it ap pears to have happened but yesterday, as we term it. However, from this cir cumstance we are often apt to confound events, as to the order of time, refer ing them to more recent or remote pe riods, according to the strength and vigour of the ideas and associations, or the contrary. In general we judge of the period of events by associated cir cumstances, particularly by visible per manent memorials. And hence it hap pens that illiterate persons have often great difficulty in assigning periods to events with any tolerable accuracy. Our readers, when they take such things in to account, and consider how difficult it must in most cases be for illiterate persons, who have frequently changed their employments, to refer such changes to any specific dates, will not feel un willing to admit, that the presumption formed against the reputed murderers of Steele, in consequence of their incor rect statements as to their places of employment four years before their trial, should have weighed very little in the decision against those unhappy men.
111. We distinguish a new place, per son, &c. from one which we remember, in a manner similar to that in which we distinguish between recollected ideas and those of imagination ; by the greater vi vidness of the impression, and the strength and readiness of the associated circumstances. If we doubt whether we have before seen a person who is newly introduced to us, we try to recal some associated circumstance, such as the time and place where we may be supposed to have seen hint ; and if this prove errone ous, we immediately infer that our doubt arises from some resemblance which he has with some one whom we then or there saw or with some one whose face is fa miliar to us.
112. The memory of children is imper fect, because the elementary rudiments of memory are not sufficiently fixed by the retentive power, nor their usual groups sufficiently formed in the mind. They are also imperfect in the use of those words and other symbols which so mate rially aid the recollection ; and in par ticular they are found very deficient in arranging facts in the order of time, judging most frequently from the vivid ness of their recollections, and not hav ing the use of those denotements of time, on which the memory principally de pends for accuracy in this branch of recol lection. In old persons, whatever be the part of the system on which the reten tive power depends, that power is most materially diminished, as also the sensi tive power, while the associative power has, in their habitual direction of it, been strengthened in its operations. Hence new impressions can scarcely be receiv ed, and seldom are retained ; while the parts which are received and retained excite old trains of associations, rather than continue those which were recently impressed. When old persons relate the incidents of their youth with great pre cision, it is rather owing to the recollec tion of many preceding recollections and relations, than to the recollection of the thing itself.
113. Memory depends greatly upon the state of the brain. Concussions, and other disorders of the brain, and the use of spirituous liquors, impair it : and it is recovered by degrees,as the causes which affected the brain are removed. In like manner dreams, which happen in a pecu liar state of the brain, viz. during sleep, vanish as soon as vigilance, a different state, takes place ; but if they be recol lected immediatelyupon waking, and thus connected with a state of vigilance, they may be remembered.
114. When a person desires to recol lect a thing that has escaped him, sup pose the name of a visible object, he re cals the visible idea, or some other asso ciate, again and agaimby avoluntary er, and thus at last brings in the required association and idea. But if the desire be very great, it changes the state of the brain, and has an opposite effect, so that the desired idea does not recur till all has subsided, perhaps not even then.
115. The excellence of memory con. sists partly in its strength and accuracy of retention, partly in the readiness of recollection. The former principally depends on the strength and accuracy of perception in attention to our sen sations, and partly upon the associative faculty ; the latter depends entirely up on the strength and peculiar biases of the operations of that power. The in tellectual faculties depend greatly up on the memory : hence, though some persons may have strong memories with weak judgments, yet no man can have a strong judgment with a weak original power ofretaining and remembering. Be fore we conclude our view of this faculty, we beg leave strongly to recommend to our younger readers, especially if they possess a philosophic cast of mind, an at tentive perusal of the very useful and in terestin chapter of Dugald Stewart on this subject, particularly those parts which relate to the improvement of the memo. ry.