But notwithstanding the fpecious 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 subdivifions of each category are no lefs imperfect. Aristotle has given some subdivisions of a few of them; and as far as he goes, his followers pretty unanimously take the fame 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, ftill the highest genus in each category could not be defined, because it is not a fpecies; 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 fenfe, or to the understanding. Thus, green, red, and blue, are very diftinct fpecies of colour; but who can exprefs in words wherein green differs from red or blue?

Without borrowing light from the ancient fyftem, we may perceive, that every definition must confift 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 diftinguish between the definition of a word, and the definition of a thing; confidering the former as the mean office of a lexicographer, but the last as the grand work of a philofopher. But what they have faid about the definition of a thing, if it has a meaning, is beyond my comprehenfion. 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 effence of any thing that exi.ts; this is impotlible, and is the vain bouft of men unconscious of the weakness of human understanding.

The works of God are all imperfectly known by us. We fee their outside, or perhaps we discover fome of their qualities and relations, by obfervation and experiment, affifted by reasoning;. but we can give no definition of the meaneft of them which comprehends its real effence. It is justly 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 precision to our notions: by a definition, we must endeavour to do it by attentive reflection upon them, by obferving minutely their agreements and differences, and especially by a right understanding 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 abuse of words, carry conviction along. with them; and 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 those 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 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 fent to his school a cock with his feathers plucked off, defiring to know whether it was a man.

man.

or not.

SECT.

SECT. 5. On the Structure of Speech.

The few hints contained in the beginning of the book concerning Interpretation, relating to the ftructure of fpeech, have been left out in treatifes of logic, as belonging rather to grammar; yet I apprehend this is a rich field of philofophical speculation. Language being the exprefs image of human thought, the analysis of the one must correfpond to that of the other. Nouns adjective and substantive, verbs active and paffive, with their various moods, tenfes, and perfons, must be expreffive of a like variety in the modes of thought. Things which are diftinguished in all languages, such as fubftance and quality, action and paffion, caufe 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 are neither the least ingenious nor the leaft ufeful part of the Peripatetic philofophy, were neglected for many ages, and lay buried in ancient manuscripts, or in books little known, till they were lately brought to light by the learned Mr Harris in his Hermes.

The definitions given by Aristotle, of a noun, of a verb, and of speech, 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 justly, that besides that kind of speech 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

which we may add, a question, a command, a promise, a contract, and many others. Thefe Aristotle 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 use, 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 reasoning.

.

SECT. 6. On Propofitions.

Mathematicians ufe the word propofition in a larger sense than logicians. A problem is called a propofition in mathematics, but in logic it is not a propofition: it is one of those speeches which are not enunciative, and which Aristotle 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 diftinguifh 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 these two are called the terms of the propofition. Hence likewise it appears, that propofitions are either affirmative or negative; and this is called their quality. All affirmative propositions have the fame quality, fo likewife have all the negative; but an affirmative and a negative are contrary in their quality.

When the subject of a propofition is a general term, the predicate is affirmed or denied, either of the whole, or of a part. Hence propofitions are distinguished into universal and particular. All men are mortal, is an univerfal propofition; Some men are learn

ed,

ed, is a particular, and this is called the quantity of the propofition. All univerfal propofitions agree in quantity, as alfo all particular: while an univerfal and a particular are faid to differ in quantity. A propofition is called indefinite, when there is no mark either of univerfality or particularity annexed to the subject: thus, Man is of few days, is an indefinite propofition; but it must be understood either as univerfal or as particular, and therefore is not a third fpecies, but by interpretation is brought under one of the other two.

There are also fingular propofitions, which have not a general term but an individual for their fubject; as, Alexander was a great conqueror. These are confidered by logicians as univerfal, because, the subject being indivifible, the predicate is affirmed or denied of the whole, and not of a part only. Thus all propofitions, with regard to quality, are either affirmative or negative; and with regard to quantity, are univerfal or particular; and taking in both quantity and quality, they are univerfal affirmatives, or univerfal negatives, or particular affirmatives, or particular negatives. These four kinds, after the days of Åristotle, came to be named by the names of the four first vowels, A, E, I, O, according to the following distich:

Afferit A, negat E, fed univerfaliter ambæ ;

Afferit I, negat 0, fed particulariter ambo.

When the young logician is thus far instructed in the nature of propofitions, he is apt to think there is no difficulty in analysing any propofition, and fhewing its fubject and predicate, its quantity and quality; and indeed, unless he can do this, he will be unable to apply the rules of logic to ufe. Yet he will find, there are fome difficulties in this analysis, which are overlooked by Aristotle altogether; and altho' they are fometimes touched, they are not removed]