general term that comprehends with man several other creatures. The whole mystery of genera and species, which make such a noise in the schools, is nothing else but abstract ideas more or less comprehensive, with names annexed to them.

This may show us why in defining words we make use of the genus, or next general word which comprehends it; which is to save the labor of enumerating the several sim ple ideas which the next general word stands for. But though defining by the genus be the shortest way, it may be doubted whether it be the best. It is not the only, and so not absolutely necessary. For definition being nothing but making another understand by words what idea the term defined stands for, a definition is best made by enumerating those simple ideas that are contained in the signification of the term defined. For to one who desired to know what idea the word man stood for, if it should be said that man was a solid extended substance, having life, sense, spontaneous motion, and the faculty of reasoning; I doubt not the meaning of the term man would be as well understood as when it is defined to be a rational animal.

To return, it is plain that general and universal are the inventions of the understanding, made by it for its own use, and concern only signs, whether words or ideas. When therefore we quit particulars, the generals that remain are only creatures of our own making, their general nature being nothing but the capacity they are put into by the understanding of signifying many particulars for the signification they have is nothing but a relation, that by the mind of man is added to them.

The next thing to be considered is, what kind of signification general words have. They do not signify one particular thing, for then they would be but proper names, nor do they signify a plurality, for man and men would then signify the same, and the grammatical

distinction of numbers be useless. That which they signify is a sort of things, and the essences of the sorts or species of things are nothing else but these abstract ideas. For having the essence of any species being that which makes any thing to be of that species, and the conformity to the idea to which the name is annexed, being that which gives a right to the name, the having the essence, and the having that conformity, must needs be the same thing; since to be of any species, and to have a right to the name of that species, is all

one.

I do not deny that nature makes many things alike; but yet we may say that the sorting of them under names is the workmanship of the understanding, taking occasion, from the similitude it observes among them, to make abstract general ideas, and to use them as patterns to which particular things agree. And when general names have any connexion with particular beings, these abstract ideas are the medium that unites them; so that the essences of species neither are nor can be any thing but those precise abstract ideas we have in our own minds. And therefore the supposed real essences of substances, if different from our abstract ideas, cannot be the essences of the species we rank things into: for two species may be one as rationally as two different essences be the essence of one species.

Nor will any one wonder that these essences are the workmanship of the understanding, who considers that complex ones are often in several men different collections of simple ideas. Nay, even in substances, where their abstract ideas seem to be taken from the things themselves, they are not constantly the same, it having been doubted whether the fœtus were a man, so far as that it hath been debated whether it were or were not to be nourished and baptized. So that in truth every distinct abstract idea is a distinct essence. But since the essences of things are thought by some

to be wholly unknown, it may not be amiss to consider the several significations of the word essence.

1. The proper original signification of the word, as is evident from the formation of it, is the being of any thing, whereby it is what it is: thus the internal constitution of things, whereon their discoverable qualities depend, may be called their essence.

2. The most familiar use of the word essence is its application to the artificial constitution of genus and species, and then it denotes that abstract idea with which any class of things agrees.

These two sorts of essences may be termed real and nominal.

The name of any kind or sort of things always expresses the nominal essence. Concerning the real essence of substances there are two opinions. Some use the word essence for they know not what; and suppose a certain number of essences, according to which all natural things are made, and of which each partakes, so as to be of this or that species. Others, more rationally, suppose all natural things to have a real but unknown constitution of their insensible parts, whence are derived those sensible qualities by which we distinguish them into sorts. The former of these notions has, I think, very much perplexed the knowlége of natural things. The frequent production of monsters in all the species of animals is a difficulty that cannot consist with this hypothesis; since it is as impossible that two things, partaking of the same real essence, should have different properties, as that the properties of two circles should be different. Besides, the supposition of unknown essences is so wholly useless, as to be a sufficient reason for our rejecting it, and contenting ourselves with such essences as come within the reach of our knowlege, which, when seriously considered, will be found to be nothing else than those abstract complex ideas to which we have annexed distinct general names. The real and nominal

essence is the same in simple ideas and modes, but different in substances: thus, a figure including a space between three lines, is the real as well as nominal essence of a triangle; it being not only the abstract idea, to which the general name is annexed, but the very being of the thing itself, the foundation from which all its properties flow: whereas, the two es sences of the ring on my finger are apparently different; for the real constitution of its inseparable parts, on which depend the properties of color, weight, fusibility, &c. makes it gold; which name is therefore its nominal essence. We are told that essences are all ingenerable and incorruptible: now this cannot be true of the real constitutious of things, which begin and perish with the things themselves; for all things that exist, except their Author, are liable to change. What is grass to-day, is to-morrow the flesh of a sheep, and soon becomes part of a man, where it is evident that the real essence perishes with each change.

But essences considered as ideas established in the mind, with names annexed, are supposed to remain the same, whatever mutations the particular substances are liable to. The ideas of man and horse remain the same, whatever change the species may undergo; so that the essence of a species may remain safe and entire, without the existence of one individual of the kind. Were there now no circle actually existing in the world, the idea annexed to the name would not cease to be what it is, and to show what figure has a right to the name of circle. Though there had never been in nature such a beast as an unicorn, yet supposing the name to denote a complex abstract idea that has no inconsistency in itself, the essence of an unicorn is as intelligible, and the idea as permanent, as that of a man. Hence it is evident that the doctrine of the immutability of essences proves them to be only abstract ideas; and is founded on the relation established between them and certain sounds as signs of

them, which will always be true, as long as the same name can have the same signification.

CHAPTER IV.

Of the Names of Simple Ideas.

Though words signify nothing immediately but ideas in the mind of the speaker, yet we shall find that the names of simple ideas, mixed modes, and natural substances have each of them something peculiar.

1. The names of simple ideas and substances intimate some real existence; but the names of mixed modes terminate in the idea that is in the mind.

2. The names of simple ideas and modes signify always the real as well as nominal essence of their species; but the names of natural substances signify rarely, if ever, any thing but the nominal essences of those species.

3. The names of simple ideas are not capable of any definitions, the names of all complex ideas are. It has not hitherto, as I know, been taken notice of by any body, what words are, and what are not, capable of being defined, whilst some demand definitions of terms that cannot be defined, and others rest satisfied with an explication made by a more general word and its restriction, when after such definition, those who hear it have no more a clear conception of the meaning of the word than they had before.

I will not trouble myself to prove that if the terms of one definition were still to be defined by others, the process would be infinite; but I shall show from the nature of ideas, and the signification of words, why some names can, and others cannot be defined, and which they are.

I think it is agreed that a definition is the showing the meaning of one term by others not synonimous. The names of simple ideas are incapable of being defined, because the several terms of a definition signi