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like those glasses whereby we bebold such objects distinctly as, by reason of their smallness or their great distance, appear in confusion to the naked eye: so the telescope discovers to us distant wonders in the heavens, and shews the milky way, and the bright cloudy spots in a very dark sky, to be a collection of little stars, which the eye unassisted beholds in mingled confusion. So when bodies are too small for our sight to survey them distinctly, then the microscope is at hand for our assistance, to shew us all the limbs and features of the most minute animals, with great clearness and distinction.
II. W ben we are taught by logic to view a thing completely in all its parts by the help of divisioo, it has ihe use of an anatomical knife, which dissects an animal body, and separates the veins, arteries, nerves, muscles, membranes, &c. and shews us the several parts which go to the composition of a complete ani. mal.
III. When logic instructs us to survey an object comprehensively in all the modes, properties, rela. tions, faces, and appearances of it, it is of the same use as a terrestrial globe, which turning round on its axis represents to us all the variety of land and seas, kingdoms and nations on the surface of the earth in a very short succession of time, shews the situation and various relations of them to each other, and gives a comprehensive view of them in miniature.
IV. When this art teaches us to distribute any exteusive idea into its different kinds or species, it may be compared to the prismatic glass, that receives the sun-beams, or rays of light, which seem to be uniform when falling upon it, but it separates and distributes them into their different kinds and colours, and ranks them in their proper succession.
Or if we descend to subdivisions and subordinate ranks of being, then distribution may also be said to form the resemblance of a natural tree, wherein the genus or general idea stands for the root or stock, and the several kinds of species, and individuals, are distributed abroad, and represented in their dependence and connection, like the several boughs, branches,
and lesser shouts. For instance, let animal be the root of a logical tree, the resemblance is seen by mere inspection, though the root be not placed at the bote tom of the page.
Caterpillar, &c. The same similitude will serve also to illustrate the division and subdivision of an integral whole, into its several parts.
When logic directs us to place all our ideas in a proper method, most convenient hotb for instruction and memory, it doth the same service as the cases of well contrived shelves in a large library, wherein folios, quartos, octavos, and lesser volumes, are disposed in such exact order, under the particular heads of divinity, history, inathematics, ancient and miscellaneous learning, &c. that the student knows where to find every book, and has them all as it were with
in his command at once, because of the exact order wherein they are placed.
The nian who has such assistances as these at hand, in order to manage his conceptions and regulate his ideas, is well prepared to improve his kuowledge, aud to join those ideas together in a regular: manner by judgment, which is the second operation of the mind, and will be the subject of the second part of logic.
THE SECOND PART OF LOGIC.
OF JUDGMENT AND PROPOSITION. WHEN the mind has got acquaintance with things by framing ideas of them, it proceeds to the next ope. ration, and that is, to compare these ideas together, and to join them by afirmation, or disjoia them by negation, according as we find them to agree or disa gree. This act of the mind is called judgment; as when we have by perception obtained the ideas of Plato, a philosspher, man, innocent, we form these judgments: Plato was a philosopher, no man is innocent,
Some writers have asserted, that judgment consists in a mere perception of the agreement or disagreement of ideas. But I rather think there is an act of the will (at least in most cases) necessary to form a judgment: for though we do perceive or think we perceive ideas to agree or disagree, yet we may sometimes refrain from judging or assenting to the perception, for fear lest the perception should.not be sufficiently clear, and we should be mistaken: and I am well assured at other times, that there are multitudes of judgments formed, and a firm assent given to ideas joined or disjoined, before there is any clear perception whether they agree or disagree; and this is the reason of so many false judgments, or mistakes among
Both these practices are a proof that judga ment has something of the will in it, and does not merely consist in perception, since we sometimes
judge (tbough unhappily) without perceiving, and sometimes we perceive without immediate judging.
As an idea is the result of our conception or apa prehension, so a proposition is the effect of judgment. The foregoing sentences which are examples of the act of judgment, are properly called proposi. tions. Plato was a philosopher, &c.
Here let us consider,
1. The general nature of a proposition, and the parts of which it is composed.
2. The various divisions or kinds of propositions. 3. The springs of false judgment, or the doctrine of prejudices.
4. General directions to assist us in judging aright.
5. Special rules to direct us in judging particular objects.
CHAP. I. OF THE NATURE OF A PROPOSITION AND ITS SEVE.
RAL PARTS. A PROPOSITION is a sentence wherein two or more ideas or terms are joined or disjoined by one affirmation or negation, as Plato was a philosopher : every angle is formed by two lines meeting : no man living on earth can be completely happy. When there are ever so many ideas or terms in the sentence, yet if they are joined or disjoined merely by one single affirmation or negation, they are properly calla ed but one proposition, though they may be resolved into several propositions which are implied therein, as will appear hereafter.
In describing a proposition, I use the word terms as well as ideas, because, when mere ideas are joined in the mind without words, it is rather called a judge ment; but when clothed with words, it is called a proposition, even though it be in the mind only, as well as when it is expressed by speaking or writing.
There are three things which go to the nature and constitution of a proposition, viz. the subject, the predicate, and the copula. The subject of a proposition is that concerning which any thing is affirmed or denied: so Plato, angle, man living on earth, are the subjects of the foregoing propesitions.
The predicate is that which is affirmed or denied of the subject : so philosopher is the predicate of the first proposition ; formed by two lines meeting, is the predicate of the second ; capable of being completely happy, is the proper predicate of the third.
The subject and predicate of a proposition taken together are called ihe matter of it; for these are the materials of which it is made.
The copula is the form of a proposition; it represents the act of the mind afirming or denying, and it is expressed by these words, am, art, is, are, &c. or, am not, art not, is not, are not, &c.
It is not a thing of importance enough to create a dispute, whether the words no, none, not, never, &c. which disjoin the idea or terms in a negative proposition, shall be called a part of the subject of the copula, or of the predicate. Sometimes, perhaps, they may seem most naturally to be included in one, and sometimes in another of these, though a proposition is usually denominated attirinative or negative by its copula, as hereafter.
Note 1. Wbere each of these parts of a proposition is not expressed distinctly in so many words, yet they are all understood, and implicitly contained therein ; as Socrates disputed, is a complete proposition, for it signifies Socrates was disputing. So I die, signifies I am dying. I can write, i. e. I am able to write. Iu Latin and Greek one single word is many times a complete proposition.
Note 2. These words, am, art, is, &c. when they are used alone without any other predicate, siguify both the act of the mind judging, which includes the copula, and signify also actual existence, which is the predicate of that proposition. So Rome is, signifies Rome is existent; there are some strange monsters, that is, some strange monsters are existent: Carthage is no more, i. e. Carthage has no being.
Note 3. The subject and predịcate of a proposition