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the Greek language; but in English or Latin they adulterate the language. Yet so fond were the schoolmen of distinctions of this kind, that they added to Aristotle's enumeration, an impulsive cause, an exemplary cause, and I don't know how many more. We seem to have adopted into English a final cause; but it is merely a term of art, borrowed from the Peripatetic philosophy, without necessity or use for the English word end is as good as final cause, though not so long nor so learned.
SECT. 4. On Definitions.
It remains that we make some remarks on Aristotle's definitions, which have exposed him to much censure and ridicule. Yet I think it must be allowed, that in things which need definition and admit of it, his definitions are commonly judicious and accurate; and had he attempted to define such things only, his enemies had wanted great matter of triumph. I believe it may likewise be said in his favour, that until Locke's essay was wrote, there was nothing of importance delivered by philosophers with regard to definition, beyond what Aristotle has said upon that subject.
He considers a definition as a speech declaring what a thing is. Every thing essential to the thing defined, and nothing more, must be contained in the definition. Now the essence of a thing con
sists of these two parts: First, What is common to it with other things of the same kind; and, secondly, What distinguishes it from other things of the same kind. The first is called the genus of the thing, the second its specific difference. The definition therefore consists of these two parts. And for finding them, we must have recourse to the ten categories; in one or other of which every thing in nature is to be found. Each category is a genus, and is divided into so many species, which are distinguished by their specific differences. Each of these species is again subdivided into so many species, with regard to which it is a genus. This division and subdivision continues until we come to the lowest species, which can only be divided into individuals, distinguished from one another, not by any specific difference, but by accidental differences of time, place, and other circum
The category itself being the highest genus, is in, no respect a species, and the lowest species is in no respect a genus; but every intermediate order is a genus compared with those that are below it, and a species compared, with those above it. To find the definition of any thing, therefore, you must take the genus which is immediately above its place in the category, and the specific difference by which it is distinguished from other species of the same genus. These two make a perfect definition. This I take to be the substance of Ari
stotle's system; and probably the system of the Pythagorean school before Aristotle, concerning definition.
But notwithstanding the specious appearance of this system, it has its defects. Not to repeat what was before said of the imperfection of the division of things into ten categories, the subdivisions of each category are no less imperfect. Aristotle has given some subdivisions of a few of them; and, as far as he goes, his followers pretty unanimously take the same road. But when they attempt to go farther, they take very different roads. It is evident, that if the series of each category could be completed, and the division of things into categories could be made perfect, still the highest genus in each category could not be defined, because it is not a species; nor could individuals be defined, because they have no specific difference. There are also many species of things, whose specific difference cannot be expressed in language, even when it is evident to sense, or to the understanding. Thus green, red, and blue, are very distinct species of colour; but who can express in words wherein green differs from red or blue?
Without borrowing light from the ancient system, we may perceive, that every definition must consist of words that need no definition; and that to define the common words of a language that have no ambiguity, is trifling, if it could be done; the only use of a definition being to give a clear
and adequate conception of the meaning of a word.
The logicians indeed distinguish between the definition of a word, and the definition of a thing; considering the former as the mean office of a lexicographer, but the last as the grand work of a philosopher. But what they have said about the definition of a thing, if it have a meaning, is beyond my comprehension. All the rules of definition agree to the definition of a word; and if they mean by the definition of a thing, the giving an adequate conception of the nature and essence of any thing that exists; this is impossible, and is the vain boast of men, unconscious of the weakness of human understanding.
The works of God are but imperfectly known by us. We see their outside; or perhaps we discover some of their qualities and relations, by observation and experiment assisted by reasoning: but even of the simplest of them we can give no definition that comprehends its real essence. It is justly observed by Locke, that nominal essences only, which are the creatures of our own minds, are perfectly comprehended by us, or can be properly defined; and even of these there are many too simple in their nature to admit of definition. When we cannot give precision to our notions by a definition, we must endeavour to do it by attentive reflection upon them, by observing minutely their agreements and differences, and especially by
a right understanding of the powers of our own minds, by which such notions are formed.
The principles laid down by Locke with regard to definition, and with regard to the abuse of words, carry conviction along with them. I take them to be one of the most important improve. ments made in logic since the days of Aristotle not so much because they enlarge our knowledge, ás because they make us sensible of our ignorance; and shew that a great part of what speculative men have admired as profound philosophy, is only a darkening of knowledge by words without understanding.
If Aristotle had understood these principles, many of his definitions, which furnish matter of triumph to his enemies, had never seen the light : let us impute them to the times rather than to the man. The sublime Plato, it is said, thought it necessary to have the definition of a man, and could find none better than Animal implume bipes; upon which Diogenes sent to his school a cock with his feathers plucked off, desiring to know whether it
was a man or not.
SECT. 5. On the Structure of Speech.
The few hints contained in the beginning of the book concerning Interpretation relating to the structure of speech, have been left out in treatises of logic, as belonging rather to grammar; yet I apprehend