Part I, Chapter 13: Important Observations in relation to the Definition of Names
AFTER having explained what is meant by the definitions of names, and how useful and necessary they are, it is important to make some observations relative to the manner of using them, to the end that they be not abused.
The first is—that we must not undertake to define all words, because this would often be useless, and it is often impossible to be done. I say that it would often be useless to define certain names, for when the idea which men have of anything is distinct, and when all those who understand the language form the same idea in hearing a word pronounced, it would be useless to define it, since it already answers the end of definition, which is, that the word be attached to a clear and distinct idea. This is the case in very simple things, of which all men have naturally the same idea, so that the words by which they are expressed, are understood in the same manner by all those who employ them; or, if at any time there be any obscurity in them, their principal attention, nevertheless, falls always on that which is clear in them; and thus those who employ them only to denote a clear idea, need not fear that they will not be understood. Such are the words,—being, thought, extension, equality, duration, or time,—and others of a similar description. For, though some have obscured the idea of time by different propositions which they have formed, and which they have called definitions, as that time is the measure of motion, according to anteriority or posteriority, nevertheless, they do not themselves rest in these definitions when they hear time spoken of, and conceive only that which others naturally conceive of it; and thus the wise and the ignorant understand the same thing, with the same facility, when it is said that a horse takes less time to go a league than a tortoise. I say, further, that it would be impossible to define all words; for, in order to define a word, we must of necessity have others which may designate the idea to which we may wish to attach that word; and if we still wish to define the words which we have employed for the explication of it, we should still have need of others, and so on to infinity. It, therefore, is necessary that we stop at some primitive terms which cannot be defined; and it would be as great a fault to wish to define too much as not to define enough, because by one or the other we should fall into that confusion which we pretend to avoid.
The second observation is, that we must not change definitions already received when we have nothing to complain of in them, for it is always more easy to make a word understood, when recognised custom, at least among the learned, has attached it to an idea, than when it is necessary to affix it to a new one, and to detach it from some other idea to which custom had joined it. Hence, it would be unwise to change the received definitions of mathematicians, unless there were any that were perplexed, and whose idea had not been designated with sufficient clearness, as, perhaps, those of the angle and of proportion may be in Euclid.
The third observation is, that when we are to define a word, we ought, as far as possible, to accommodate ourselves to custom, in not giving to words a sense altogether removed from that which they have, and which might be even contrary to their etymology: as when I say—I call a parallelogram a figure bounded by three lines,—but content ourselves, for the most part, in stripping words which have two senses of one of these, in order to attach it exclusively to the other: as heat expresses, in its common acceptation, both sensation which we have, and a quality which we imagine to be in the fire, resembling altogether that which we feel. In order to avoid this ambiguity, I may employ the name heat—in applying it to one of these ideas, and detaching it from another: as I say—I call heat the sensation which I have when I approach the fire, and giving to the name of that sensation, either a name altogether different, such as that of burning—(ardeur)—or the same name, with some addition which determines it, or which distinguishes it from heat taken from the sensation, as we might say virtual heat.
The reason of this observation is, that men having at one time attached an idea to a word, do not easily separate the two; and thus, the former idea always returning, causes them easily to forget the new, which you would give them in defining that word, so that it would be more easy to accustom them to a word which signified nothing at all: as when I say—I call bara a figure bounded by three lines—than to accustom them to strip from the word parallelogram the idea of a figure whose opposite sides are parallel, to make it signify a figure whose sides could never be parallel.
It is a mistake into which all chemists have fallen who have delighted to change the names of almost everything whereof they speak, without any advantage, and of giving them those which already signify other things which have no real relation to the new ideas with which they connect them. This has given rise to some ridiculous arguments: as that of the man who, imagining that the plague was a Saturnian evil, pretended that people would be cured of the pestilence by hanging round the neck a bit of lead (which the chemists call Saturn), upon which was engraved, on a Saturday (which also derives its name from Saturn), the figure which astronomers use to denote that planet, as if these connections, arbitrary and without reason, between the lead and the planet Saturn, and between the same planet and Saturday, and the small mark which denotes it, could have any real effects, and could cure, effectually, diseases.
But what is more intolerable, is the profanation which they make of the most sacred mysteries of religion as a veil for their pretended secrets; so far, indeed, that there are some who have been impious enough to apply what the Scripture says of true Christians,—that they are the chosen race,—the royal priesthood,—the holy nation,—the people whom God has chosen, and whom he has called out of darkness into his wonderful light,—to the chimerical brotherhood of the Rosicrucians, who are, according to them, sages who have attained to a glorious immortality, having found the means, through the philosophers’ stones, of fixing their soul in their body; inasmuch as (say they), there is no body more fixed and incorruptible than gold. We may see these reveries, and many others like them, in the examination of Fludd’s philosophy, by Gassendi, who showed that there was scarcely any character of mind worse than that of these enigmatical writers, who imagine that thoughts the most groundless, not to say false and impious, would pass for grand mysteries when clothed in forms of speech unintelligible to common men.