378 LOGIC: OR, THE RIGHT USE or REASON. 6th, Where we cannot find out the essence or essential dieer ence of any species or kind of beings that we would define, wè must content ourselves with -a collection of such chief parts or properties of it, as may best explain it so far it is known, and best distinguish it from other things : so a " marigold is a flower which hath many yellow long leaves, round a little knot of seeds in the midst, with such a peculiar stalk, &c. So if we would define silver, we say it is a white and hard metal, next in weight to gold : if we would define an elder -tree, we might say it is one among the lesser trees, whose younger branches are soft and full of pith, whose leaves are jagged or indented, and of such a particular shape, and it bears large clusters of small black berries :" so we must define water, earth, stone, a lion, an eagle, a serpent, and the greatest part of natural beings, by a collection of those properties, which according to our observation distin- guish them from all other things. This is what Mr. Locke calls nominal essences, and nominal definitions. And indeed, since the essential differences of the various natural beings or bodies round about us arise from a peculiar shape, size, motion, and situation of the small particles of which they are composed, and since we have no sufficient method to inform us what these are, we must be contented with such a sort of definition of the bodies . they compose. Here note, That this sort of definition, which is made up of mere collection of the most remarkable parts of properties, is called an imperfect definition, or a description.; whereas the de- finition is called perfect, when it is composed of the essential dif- Terence, added to the general nature or genus, 7th. The perfect definition of any being always includes the definition of the name whereby it is called, for it informs us of Ìhe sense or meaning of that word, and shews us what idea that word is affixed to : but the definition of the name does by no means include a perfect definition of the thing ; for as we have said before, a mere synonymous word, a negation of the contrary, or the mention of any one or two distinguishing pro - perties of the thing, may be a sufficient definition of the naine. Yet in those cases where the essential difference or essence of a thing is unknown, there is a definition of the name by the chief properties, and a description of the thing, are much the same. And here I think it necessary to take notice of one general sentiment, that seems to run through that excellent performance, Mr. Locke's Essay of Human Understanding, and that is, " That the essences of things are utterly unknown to us, and therefore all our pretences to distinguish the essences of things, can reach no farther than mere nominal essences; or a collection of such properties as we know ; to some of which we affix par- ticular names, and others we bundle up, several together under
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