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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 effence of any thing that exists; this is impoffible, 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 fee their outfide; or perhaps we difcover fome of their qualities and relations, by observation and experiment affifted by reafoning: but even of the fimpleft of them we can give no definition that comprehends its real effence. It is juftly obferved by Locke, that nominal effences 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 fimple in their nature to admit of definition. When we cannot give precifion to our notions by a definition, we must endeavour to do it by attentive reflection upon them, by obferving minutely their agreements and dif ferences, and especially by a right underftanding of the powers of our own minds by which fuch notions are formed.
The principles laid down by Locke with regard to definition and with regard to the abufe of words, carry conviction along with them. I take them to be one of the most important improvements made in logic fince the days of Ariftotle: not fo much because they enlarge our knowledge, as because they make us fenfible of our ignorance; and fhew that a great part of what speculative men have admired as profound philofophy, 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 feen the light let us impute them to the times rather than to the man. The fublime Plato, it is faid, thought it neceffary 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, defiring to know whether it was a man or
SECT. 5. On the Structure of Specch.
The few hints contained in the beginning of the book concerning Interpretation relating to the ftructure of fpeech, have been left out in treatises of logic, as belonging rather to grammar; yet I apprehend this is a rich field of philofophical fpeculation. Language being the exprefs image of human thought, the analysis of the one must correfpond to that of the other. Nouns adjective and fubftantive, verbs active and paffive, with their various moods, tenfes, and perfons, must be expreffive of a like variety in the modes of thought. Things that are diftinguished in all languages, fuch as fubftance and quality, action and paffion, cause and effect, must be distinguished by the natural powers of the human mind. The philofophy of grammar, and that of the human understanding, are more nearly allied than is commonly imagined.
The structure of language was pursued to a confiderable extent, by the ancient commentators upon this book of Ariftotle. Their fpeculations upon this fubject, which VOL. III. X x
are neither the least ingenious nor the leaft ufeful part of the Peripatetic philofophy, were neglected for many ages, and lay buried in ancient manufcripts, or in books little known, till they were lately brought to light by the learned Mr Harris in his Hermes.
The definitions given by Ariftotle, of a noun, of a verb, and of fpeech, will hardly bear examination. It is eafy in practice to distinguish the various parts of speech; but very difficult, if at all poffible, to give accurate definitions of them.
He obferves juftly, that befides that kind of fpeech called a propofition, which is always either true or falfe, there are other kinds which are neither true nor falfe; fuch as, a prayer, or wifh; to which we may add, a question, a command, a promife, a contract, and many others. Thefe Ariftotle pronounces to have nothing to do with his fubject, and remits them to oratory, or poetry; and fo they have remained banished from the regions of philofophy to this day: yet I apprehend, that an analysis of fuch fpeeches, and of the operations of mind which they exprefs, would be of real ufe, and perhaps would
discover how imperfect an enumeration the logicians have given of the powers of human understanding, when they reduce them to fimple apprehenfion, judgement, and reafoning.
SECT. 6. On Propofitions.
Mathematicians ufe the word propofition in a larger fenfe than logicians. A problem is called a propofition in mathematics, but in logic it is not a propofition: it is one of thofe fpeeches which are not enunciative, and which Ariftotle remits to oratory or poetry.
A propofition, according to Aristotle, is a fpeech wherein one thing is affirmed or denied of another. Hence it is easy to diftinguish the thing affirmed or denied, which is called the predicate, from the thing of which it is affirmed or denied, which is called the fubject; and thefe two are called the terms of the propofition. Hence likewife it appears, that propofitions are either affirmative or negative; and this is called their quality. All affirmative propofitions have the fame quality, fo likewife have all X X 2 negative;