Memory and Habits

Of all material things, there is none more worthy of human attention than the structure of our body and the correspondence between all the parts that compose it; and of all spiritual things, there is none whose knowledge is more necessary to us than that of our soul, and of all the relations it has indispensably with God, and naturally with the body.

It is not enough to feel or to know confusedly that the traces of the brain are linked to one another, and that they are followed by the movement of the animal spirits; that traces awakened in the brain awaken ideas in the mind, and that movements excited in the animal spirits excite passions in the will. We must, as far as possible, know distinctly the cause of all these different connections, and especially the effects they are capable of producing.

We must know their cause, because we must know Him who alone is capable of acting within us and of making us happy or unhappy; and we must know their effects because we must know ourselves as much as we can, and other men with whom we must live. Then we shall know the means to conduct ourselves and to preserve ourselves in the happiest and most perfect state one can attain, according to the order of nature and according to the rules of the Gospel; and we shall be able to live with other men, knowing exactly both the means of using them in our needs, and those of helping them in their miseries.

I do not pretend to explain in this chapter such a vast and extensive subject. I do not even pretend to do so entirely throughout this whole work. There are many things I do not yet know, and which I do not hope to know well; and there are some things I believe I know, but cannot explain. For there is no mind so small that it cannot, by meditating, discover more truths than the most eloquent man in the world could deduce.

The connection of the mind’s ideas with the brain’s traces

We must not imagine, as most philosophers do, that the mind becomes body when it is united to the body, and that the body becomes spirit when it is united to the mind. The soul is not spread throughout all the parts of the body in order to give it life and movement, as the imagination pictures it; and the body does not become capable of sensation through its union with the mind, as our false and deceptive senses seem to convince us. Each substance remains what it is; and just as the soul is not capable of extension and movements, the body is not capable of sensation and inclinations. All the alliance between mind and body that is known to us consists in a natural and mutual correspondence between the thoughts of the soul and the traces of the brain, and between the emotions of the soul and the movements of the animal spirits.

As soon as the soul receives some new ideas, new traces are imprinted in the brain; and as soon as objects produce new traces, the soul receives new ideas. Not that it considers these traces, since it has no knowledge of them; nor that these traces contain these ideas, since they bear no relation to them; nor finally that it receives its ideas from these traces, for, as we shall explain elsewhere, it is inconceivable that the mind receives anything from the body, and that it becomes more enlightened than it is by turning toward it, as philosophers claim who hold that it is by conversion to images or traces of the brain, per conversionem ad phantasmata, that the mind perceives all things.

Likewise, as soon as the soul wills that the arm be moved, the arm is moved, although it does not even know what must be done to move it; and as soon as the animal spirits are agitated, the soul finds itself moved, although it does not even know whether there are animal spirits in its body.

When I treat of the passions, I shall speak of the connection between the traces of the brain and the movements of the spirits, and of that between the ideas and the emotions of the soul, for all the passions depend on it. I must speak here only of the connection of ideas with traces, and of the connection of traces with one another.

There are three very considerable causes of the connection of ideas with traces. The first and most general is the identity of time. For it often suffices that we have had certain thoughts at the time when there were some new traces in our brain, so that these traces cannot be produced again without our having these same thoughts again. If the idea of God presented itself to my mind at the same time that my brain was struck by the sight of these three characters Iah or by the sound of this same word, it will suffice that the traces that these characters or their sound produced are awakened, so that I think of God; and I cannot think of God without some confused traces of the characters or sounds that accompanied the thoughts I had of God being produced in my brain; for, the brain never being without traces, it always has those that have some relation to what we think, although often these traces are very imperfect and very confused.

The second cause of the connection of ideas with traces, which always presupposes the first, is the will of men. This will is necessary, so that this connection of ideas with traces may be regulated and accommodated to use. For if men did not naturally have an inclination to agree among themselves to attach their ideas to sensible signs; not only would this connection of ideas be entirely useless for society, but it would also be very disorderly and very imperfect. First, because ideas are strongly linked with traces only when the spirits being agitated, they render these traces deep and durable; so that the spirits being agitated only by the passions, if men had no passion to communicate their feelings and to enter into those of others, it is evident that the exact connection of their ideas to certain traces would be very weak; since they submit themselves to these exact and regular connections only in order to communicate their thoughts to one another.

Second, the repetition of the encounter of the same ideas with the same traces being necessary to form a connection that can be preserved for a long time, since a first encounter, if not accompanied by a violent movement of animal spirits, cannot make strong connections, it is clear that if men did not wish to agree, it would be the greatest chance in the world if these encounters of the same ideas and the same traces occurred. Thus the will of men is necessary to regulate the connection of the same ideas with the same traces, although this will to agree is not so much an effect of their choice and their reason as an impression of the author of nature who has made us all for one another, and with a very strong inclination to be united in spirit as much as we are by the body.

The third cause of the connection of ideas with traces is nature, or the constant and immutable will of the Creator. There is, for example, a natural connection, which does not depend on our will, between the traces produced by a tree or a mountain that we see, and the ideas of trees or mountains; between the traces produced in our brain by the cry of a man, or of an animal that suffers, and that we hear complaining, the expression on the face of a man who threatens us or who fears us, and the ideas of pain, strength, weakness, and even between the feelings of compassion, fear and courage that are produced in us.

These natural connections are the strongest of all; they are generally similar in all men, and they are absolutely necessary for the preservation of life. That is why they do not depend on our will: for if the connection of ideas with sounds and certain characters is weak and very different in different countries, it is because it depends on the weak and changeable will of men; and the reason why it depends on it is because this connection is not absolutely necessary for living, but only for living as men who must form a reasonable society among themselves.

It must be well noted here that the connection of ideas that represent to us spiritual things distinct from us, with the traces of our brain, is not natural and cannot be; and, consequently, it is or can be different in all men, since it has no other cause than their will and the identity of time of which I spoke earlier. On the contrary, the connection of the ideas of all material things with certain particular traces is natural; and consequently, there are certain traces that awaken the same idea in all men. One cannot doubt, for example, that all men have the idea of a square at the sight of a square, because this connection is natural; but one can doubt that they all have the idea of a square when they hear this word square pronounced, because this connection is entirely voluntary. One must think the same of all traces that are linked with the ideas of spiritual things.

But, because the traces that have a natural connection with ideas touch and apply the mind, and consequently render it attentive, most men have enough facility to understand and retain sensible and palpable truths, that is, the relations that exist between bodies; and, on the contrary, because the traces that have no other connection with ideas than that which the will has placed there do not strike the mind vividly, all men have enough difficulty in understanding and even more in retaining abstract truths, that is, the relations that exist between things that do not fall under the imagination. But when these relations are somewhat complex, they appear absolutely incomprehensible, principally to those who are not accustomed to them, because they have not strengthened the connection of these abstract ideas with their traces by continual meditation; and although others have perfectly understood them, they forget them in a short time, because this connection is almost never as strong as the natural ones.

It is so true that all the difficulty one has in understanding and retaining spiritual and abstract things comes from the difficulty one has in strengthening the connection of their ideas with the traces of the brain, that when one finds a way to explain by the relations of material things those that exist between spiritual things, one makes them easily understood, and imprints them in such a way in the mind, that not only is one strongly persuaded of them, but also one retains them with great facility. The general idea that was given of the mind in the first chapter of this work is perhaps a fairly good proof of this.

On the contrary, when one expresses the relations that exist between material things in such a way that there is no necessary connection between the ideas of these things and the traces of their expressions, one has great difficulty in understanding them and one easily forgets them.

Those, for example, who begin the study of algebra or analysis can understand algebraic demonstrations only with great difficulty, and when they have once understood them, they do not remember them for long, because squares, for example, parallelograms, cubes, solids, etc., being expressed by aa, ab, a³, abc, etc., whose traces have no natural connection with their ideas, the mind finds no hold to fix their ideas and to examine their relations.

But those who begin common geometry conceive very clearly and very quickly the small demonstrations that are explained to them, provided they understand very distinctly the terms used, because the ideas of square, circle, etc., are naturally linked with the traces of the figures they see before their eyes. It even often happens that the mere exposition of the figure used in the demonstration makes them understand it sooner than the discourses that explain it, because words being linked to ideas only by an arbitrary institution, they do not awaken these ideas with enough promptness and clarity to easily recognize their relations, for it is principally because of this that there is difficulty in learning the sciences.

One can recognize in passing from what I have just said, that those writers who fabricate a great number of new words and new figures to explain their views often produce quite useless works. They believe they make themselves intelligible, when in fact they make themselves incomprehensible. “We define all our terms and all our characters,” they say, “and others must agree to them.” It is true, others agree to them voluntarily, but their nature rebels against it. Their ideas are not attached to these new terms; because usage, and much usage, is needed for that. The authors may have this usage, but the readers do not. When one pretends to instruct the mind, it is necessary to know it; because one must follow nature and not irritate or shock it.

One should not, however, condemn the care that mathematicians take to define their terms, for it is evident that they must be defined to remove ambiguities; but, as much as possible, one must use terms that are received or whose ordinary meaning is not far removed from that which one intends to introduce, and this is not always observed in mathematics.

Nor does one claim, by what has just been said, to condemn algebra, such principally as Mr. Descartes restored it; for although the novelty of some expressions of this science at first causes some difficulty for the mind, there is so little variety and confusion in these expressions, and the help that the mind receives from them surpasses so much the difficulty it has encountered, that one does not believe that a way of reasoning and of expressing one’s reasonings could be invented that accommodates itself better to the nature of the mind and that could carry it further in the discovery of unknown truths. The expressions of this science do not divide the capacity of the mind; they do not burden the memory; they abbreviate in a wonderful way all our ideas and all our reasonings, and they even render them in some way sensible through use. Finally, their usefulness is much greater than that of expressions, although natural, of drawn figures of triangles, squares and other similar things that cannot serve in the research and exposition of somewhat hidden truths: but enough has been said about the connection of ideas with the traces of the brain; it is appropriate to say something about the connection of traces with one another, and consequently about that which exists between the ideas that correspond to these traces.

The reciprocal connection between these traces

This connection consists in that the traces of the brain are so well linked with one another that they cannot be awakened without all those that were imprinted at the same time. If a man, for example, finds himself at some public ceremony, if he notices all the circumstances and all the principal persons who attend, the time, the place, the day and all the other particulars, it will suffice that he remembers the place, or even some other less remarkable circumstance of the ceremony, to represent to himself all the others. That is why when we do not remember the principal name of a thing, we designate it sufficiently by using a name that signifies some circumstance of that thing. As not being able to remember the proper name of a church, we can use another name that signifies something that has some relation to it. We can say: it is that church where there was so much crowding, where Mr. … was preaching, where we went on Sunday; and not being able to find the proper name of a person, or it being more appropriate to designate him in another way, one can mark him by that pockmarked face, that tall well-built man, that little hunchback, according to one’s inclinations toward him, although one is wrong to use words of contempt.

Now the mutual connection of traces, and consequently of ideas with one another, is not only the foundation of all the figures of rhetoric, but also of an infinity of other things of greater consequence in morals, in politics, and generally in all the sciences that have some relation to man, and consequently of many things that we shall speak of in the sequel.

The cause of this connection of several traces is the identity of the time at which they were imprinted in the brain, for it suffices that several traces have been produced at the same time, so that they can no longer be awakened except all together, because the animal spirits finding the path to all the traces that were made at the same time, find them, they continue their way there because they pass more easily there than through the other parts of the brain: this is the cause of memory and of bodily habits that we share with animals.

These connections of traces are not always joined with emotions of the spirits, because all the things we see do not always appear to us as good or bad. These connections can also change and break, because not being always necessary for the preservation of life, they must not always be the same.

But there are in our brain traces that are naturally linked with one another, and also with certain emotions of the spirits, because this is necessary for the preservation of life, and their connection cannot break, or cannot break easily, because it is good that it always remains the same. For example, the trace of a great height that one sees below oneself, and from which one is in danger of falling, or the trace of some great body that is ready to fall on us and crush us, is naturally linked with that which represents death to us, and with an emotion of the spirits that disposes us to flight and to the desire to flee. This connection never changes, because it is necessary that it always be the same, and it consists in a disposition of the fibers of the brain that we have from birth.

All connections that are not natural can and must be broken, because the different circumstances of times and places must change them, so that they are useful for the preservation of life. It is good that partridges, for example, flee from men who have guns, in places or at times when they are hunted; but it is not necessary that they flee them in other places and at other times. Thus, for the preservation of all animals, it is necessary that there be certain connections of traces that can be formed and destroyed easily; that there be others that can be broken only with difficulty, and finally others that can never be broken.

It is very useful to carefully investigate the different effects that these different connections are capable of producing; for these effects are very numerous and of great consequence for the knowledge of man.

Memory

To explain memory, it suffices to understand well this truth: that all our different perceptions are attached to the changes that occur in the fibers of the principal part of the brain in which the soul more particularly resides, because this single principle being supposed, the nature of memory is explained. For just as the branches of a tree that have remained bent in a certain way for some time, preserve some facility to be bent again in the same manner, so the fibers of the brain, having once received certain impressions by the course of the animal spirits and by the action of objects, keep for quite a long time some facility to receive these same dispositions. Now memory consists only in this facility, since one thinks of the same things when the brain receives the same impressions.

As the animal spirits act sometimes more and sometimes less strongly on the substance of the brain, and as sensible objects make much greater impressions than the imagination alone, it is easy to recognize from this why we do not remember equally all the things we have perceived; why, for example, what we have perceived several times ordinarily represents itself to the soul more clearly than what we have perceived only once or twice; why we remember more distinctly the things we have seen than those we have only imagined; and thus why we shall know better, for example, the distribution of veins in the liver after having seen it once in the dissection of that part than after having read it several times in an anatomy book, and other similar things.

If one wishes to reflect on what was said earlier about the imagination and on the little that has just been said about memory, and if one is freed from the prejudice that our brain is too small to preserve vestiges and impressions in very great number, one will have the pleasure of discovering the cause of all those surprising effects of memory, of which Saint Augustine speaks with such admiration, in the tenth book of his Confessions. And one does not wish to explain these things at greater length, because one believes that it is more appropriate for each person to explain them to himself by some effort of mind; because the things one discovers by this means are always more agreeable, and make a greater impression on us than those one learns from others.

Habits

For the explanation of habits, it is necessary to know the manner in which one has reason to think that the soul moves the parts of the body to which it is united. Here it is.

There is always in some parts of the brain many animal spirits very agitated by the heat of the heart from which they have issued, and all ready to flow into the places where they find the passage open.

All the nerves end at the reservoir of these spirits, and the soul has the power to determine their movement and to conduct them through these nerves into all the muscles of the body. These spirits having entered there, they swell them, and consequently they shorten them; thus they move the parts to which these muscles are attached.

One will not have difficulty in persuading oneself that the soul moves the body in the manner just explained, if one takes note that when one has been a long time without eating, one may wish to give certain movements to one’s body, one cannot succeed, and one even has some difficulty in standing on one’s feet. But if one finds means to cause something very spiritous, like wine or some other similar nourishment, to flow into one’s heart, one immediately feels that the body obeys with much more ease, and one moves oneself in all the ways one wishes. For this single experiment makes it, it seems to me, sufficiently clear that the soul could not give movement to its body for lack of animal spirits, and that it is by their means that it regains its empire over it.

The swellings of the muscles are so visible and so sensible in the agitations of our arms and of all the parts of our body, and it is so reasonable to believe that these muscles can swell only because some body enters them, just as a balloon can grow and swell only because air or something else enters it, that it seems one cannot doubt that the animal spirits are pushed from the brain, through the nerves, into the muscles, to swell them and to produce there all the movements we wish: for a muscle being full, it is necessarily shorter than if it were empty. Thus it pulls and moves the part to which it is attached, as one can see explained at greater length in the books on the Passions and on Man by Mr. Descartes. This explanation is not, however, given as perfectly demonstrated in all its parts. To make it entirely evident, there are still several things to be desired, about which it is almost impossible to gain clarity. But it is also quite useless to know them for our subject; for whether this explanation is true or false, it is nonetheless equally useful for making known the nature of habits, because if the soul does not move the body in this manner, it necessarily moves it in some other way that is sufficiently similar to draw from it the consequences that we draw.

But, in order to follow our explanation, it must be noted that the spirits do not always find the paths through which they must pass sufficiently open and free, and that this causes us, for example, to have difficulty in moving the fingers with the speed necessary to play musical instruments, or the muscles that serve for pronunciation to pronounce the words of a foreign language; but that little by little the animal spirits, by their continual course, open and smooth these paths, so that with time they find no more resistance there. Now, it is in this facility that the animal spirits have in passing into the members of our body that habits consist.

It is very easy, according to this explanation, to resolve an infinity of questions concerning habits, such as, for example, why children are more capable of acquiring new habits than older persons; why it is very difficult to lose old habits; why men, by dint of speaking, have acquired such great facility in this that they pronounce their words with incredible speed, and even without thinking, as happens only too often to those who say prayers that they have been accustomed to say for several years. However, to pronounce a single word, several muscles must be moved at the same time in a certain time and in a certain order, such as those of the tongue, lips, throat and diaphragm. But one will be able, with a little meditation, to satisfy oneself on these questions and on several others very curious and quite useful; and it is not necessary to dwell on them.

It is visible from what has just been said, that there is much resemblance between memory and habits, and that in a sense memory can pass for a kind of habit. For, just as bodily habits consist in the facility that the spirits have acquired in passing through certain parts of our body; so memory consists in the traces that the same spirits have imprinted in the brain, which are the cause of the facility we have in remembering things. So that, if there were no perceptions attached to the courses of the animal spirits nor to these traces, there would be no difference between memory and other habits. It is not also more difficult to conceive that animals, although without a soul and incapable of any perception, remember in their manner the things that have made an impression in their brain, than to conceive that they are capable of acquiring different habits; and after what I have just said about habits, I do not see that there is much more difficulty in representing to oneself how the members of their body acquire little by little different habits than in conceiving how a newly made machine does not play so easily as when it has been used for some time.