Cursus Philosophicus Thomisticus, Secunda Pars Artis Logicae

A special difficulty concerns certain signs that are accommodated to signify something not by a public institution—that is, one proceeding from public authority—but merely by the will of private individuals who frequently use them for signification. Since the whole force of signification depends on use and frequency, the doubt remains whether this use and frequency signify in a natural way or by signification imposed at will.

THERE IS, THEN, ONE CONCLUSION: If custom regards some sign by assigning and proposing it as a sign, that sign, founded on custom, will be by imposition. But if custom does not propose or institute something as a sign, but there is merely the use of a thing and something is taken as a sign because of that use, such a sign is reduced to natural signification.

Thus custom can either be the cause of a sign, as when a people by its custom introduces and proposes a word to signify something; or it can be an effect that guides us to know its cause. For example, frequently seeing a dog accompany someone makes clear that the person is its master; and the custom of eating on tablecloths makes a meal known to us when we see tablecloths laid out. In general, nearly every induction is based on the frequency and custom by which we see something happen often.

THE FIRST PART of the conclusion is proved from St. Thomas, Summa Theologiae I–II, q. 97, a. 3, where he teaches that custom has the force of law. Therefore custom that introduces something to signify does so by the same authority by which the law itself would introduce it as a sign. If a word is proposed by public law as a sign, it is truly a sign by imposition, because it is instituted by public authority. Therefore custom, which takes the place of law and has the authority of law, likewise constitutes a sign by imposition. In this way we see many words introduced into public use to signify things they did not signify before, because they were not in use; and many words no longer signify what they once signified, because they have fallen into disuse. Therefore, of such a sign arising from custom, the word ex—which denotes the efficient cause according to the usage and consent of the people—must be understood in the same way as of a sign by imposition.

THE SECOND PART of the conclusion is proved because custom, insofar as it is an effect, leads us to know its cause, just as other effects reveal their causes; and custom does so more than other effects, because the frequency of producing something confirms that it is the effect of such a cause. But every effect represents its cause insofar as it proceeds from that cause and thus has some agreement and proportion with it. Therefore such signification is founded on something natural, namely, the effect’s proceeding from its cause and its agreement with that cause. Hence custom, as an effect that grounds signification, is reduced to a natural cause. Thus the Philosopher says that pleasure is a sign of a habit that has been generated, because we take pleasure in what we do habitually, owing to its agreement with what we have made habitual.

THE ARGUMENTS ARE RESOLVED.

First it is argued that custom is not a natural effect, but a moral and free one; therefore it cannot ground the account of a natural sign.

The consequence is clear, because something cannot be called a natural sign more than its cause, from which it has being. Therefore, if the sign does not come from a natural cause, it will not be called a natural sign either.

The antecedent is proved as follows. Custom is the same as mos (“customary practice”), from which acts are called moral or human, as St. Thomas teaches in Summa Theologiae I–II, q. 1, a. 3. Therefore custom among human beings is not a natural but a moral effect; thus a sign founded on custom is founded on something moral and free, which posits nothing real in external things but only an extrinsic denomination. A sign founded on an extrinsic denomination cannot be a natural sign.

THE ANSWER IS that, first of all, speaking generally, custom is found not only among human beings but also among brute animals that act by natural instinct. Hence St. Thomas, Metaphysics I, lecture 1,¹ shows that brute animals can be teachable and can become accustomed to doing or avoiding something through another’s instruction. Thus not every custom is a human act and it can ground a natural sign, as the custom of a dog following someone is a sign that the person is its master.

Second, speaking of human custom, although it proceeds from a free cause and is therefore denominated a free effect, the formal account of signifying is not some free assignment. Rather, it is the frequency and repetition of acts themselves, and these signify naturally. For what constitutes a sign arising from custom is not a moral—that is, extrinsic—assignment, which denominates only morally, but the intrinsic procession of the acts, their frequency, and their multiplication. Therefore signification belongs to it naturally by reason of this repetition of acts, even though the acts themselves are free in themselves. Likewise, multiplied free acts generate a habit as a natural, not free, effect, because the multiplication of the acts itself does not relate freely to generating the habit; nor does it relate freely to signifying by the force of repeated acts.

Second it is argued: If a sign arising from custom represents naturally because it is an act repeated more often, then every custom will be a sign of something, because every custom is an effect proceeding from repeated acts. But this is false: many customs signify nothing, such as the custom of sleeping at night, eating at midday, approaching a fire in winter, and infinitely many others. Therefore custom does not signify merely because it is the effect of some cause, and thus it will not be a natural sign.

This is confirmed because a sign arising from custom can cease to be a sign without any intrinsic change, namely, through the mere disuse or omission of using it. Therefore it is not a natural sign. The consequence is clear, because a natural sign must be constituted by something intrinsic and natural; therefore it cannot be lost through the mere suspension of voluntary use, but only through some real opposite.

THE ANSWER IS that for something to be a sign arising from custom, it must also have what belongs to the account of a sign: it must be ordered to something that is made better known through custom itself, not merely because it is an effect, but because it is frequent. If, however, something is not taken as a means to something else—as tablecloths are to a meal—or if it is not made better known by its frequent occurrence—as someone’s being a dog’s master is not made better known by the dog’s repeated following—then it is not a sign arising from custom, although there is a custom.

To the confirmation, we reply that a sign arising from custom does not cease merely through a suspension that removes an institution, but through a suspension that removes the multiplication of acts and frequency of use. Since the representation of a sign arising from custom is founded on the very multiplication of acts that constitutes the custom, when that multiplication is removed, the foundation of the sign is removed. Thus the determination left by multiplication is destroyed through the privation of its opposite, just as the habit of science is lost through forgetting. This is especially so because something positive always intervenes in losing memory or custom, insofar as other and other objects succeed one another, by which earlier things gradually fall away from memory, disposing one to an opposite act or preventing the memory and custom themselves from taking root.

Finally it is argued: A sign arising from custom can result from will alone, without any multiplication of acts; therefore at least in that case it does not represent as a natural sign.

The antecedent is proved because by the mere accommodation and designation of human beings, a statue or image is set up to represent a saint; or an actor represents a king or Caesar not by public decree or human custom, but by that person’s particular act alone.

This is confirmed because, if the teaching given is true, it follows that words signify naturally what they have been imposed to signify. For even if the imposition were removed from the word “human being,” it would still represent a human being to us because of the custom we have. Therefore it represents naturally by custom.

Finally, a natural sign is one that signifies the same thing to everyone. But a sign arising from custom does not signify the same thing to everyone, only to those who know the custom, just as a sign by imposition signifies only to those who know the imposition. Therefore it does not represent naturally.

THE ANSWER IS that any image, insofar as it is an image, represents only that to whose likeness it is expressed, namely, its own idea, whatever that may be. If, however, through human usage it is accommodated to represent an object other than its own idea, that accommodation or designation with respect to that object constitutes the image as a sign by imposition, if the designation is made by public authority, or as a sign by custom, if it is made through human usage. If someone by a single act, without custom, sets something up to represent another thing, such a designation will be a kind of incipient custom. Thus it will represent to that person in the manner of a sign arising from custom or as a mnemonic prompt. For this reason an actor is also said to represent a king either by signification arising from custom or as a mnemonic prompt, because people agree that when they see someone representing such a person, they are reminded of the one represented. Likewise, through a pact or agreement among some people, something can be designated as a sign or a mnemonic prompt; all this is reducible to a sign by imposition or by custom.

To the confirmation, we reply that words signify per se only by imposition, but per accidens through custom; this is to signify naturally, not in itself, but only with respect to those among whom the custom is known. It is no contradiction for two modes of signifying to belong to the same thing according to distinct formalities. Thus, when one is removed, the other remains; so the same sign is never formally both natural and by imposition, although materially the signs are the same, that is, they belong to the same subject.

As for the claim that a natural sign is one that signifies the same thing to everyone, this is understood of what is a natural sign simply, because nature is the same for all. Custom, however, is like another nature, but is not nature itself; therefore it signifies to everyone among whom the custom exists, not to everyone without qualification. In this way it is something less perfect in the genus of natural sign, just as custom itself is something imperfect in the genus of nature.