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defined. Whatever is affirmed or denied of the genus, may be affirmed or denied of the species, &c.
Metaphysical canons are such as these; final causes. belong only to intelligent agents. If a natural and neceffary cauie operate, the effect will follow, &c. and there are large catalogues of many more in each distinct fcience.
Now it bas been the custom of those who teach logic or rhetoric, to direct their disciples, when they want an argument, to coufult the several topics which are fuired to their lubject of discourse, and 10 rummage over the definitions, divifions and canons that belong to each topic. This is called the invention of an argument, and is taught with much solemnity in some Ichools.
I grant there may be good use of this practice for persons of a lower genius, when they are to compole any discourse for the public; or for those of superior parts to refresh their memory, and revive their acquaintance with a subject which has been long absent from their thoughts, or when their natural spirits labour under indisposition and langour; but when a man of moderate fagacity has made himself master of his theme by just diligence and inquiry, he has feldom need to run knocking at the doors of all the topics, that he rnay furnith himself with argument or matter of speaking ; and indeed it is only a man of sense and judgment that can use common places, or topics well; for amongst this variety he only knows what is fit to be left out, as well as what is fit to be spoken.
By some logical writers this business of topics and invention is treated of in such a manner with mathemarical figures and diagrams, filled with the barbarous tech. nical words, Napcas, Nipcis, Ropcos, Nofrop, &c. as though an ignorant lad. were to be led mechanically in certain artifical harnesses and trammels to find out arguments to prove or refute any proposition whatsoever, without any rational knowledge of the ideas. Now there is no need to throw words of contempt on such a practice ; the very description of it carries reproof.and. ridicule in abundance.
Of feveral Kınds of Arguments and Demonftrations. .
E proceed now to the division of syllogisms acVV cording to the middle term ; and in this part of our treatise the syllogisms themselves are properly called arguments, and are thus distributed
I. Arguments are called Grammatical, Logical, Metaphysical, Physical, Moral, Mechanical, Theological, &c. according to the art, science or subject, whence the middle term or topic is borrowed. Thus if we prove that no man should steal from his neighbour because the scripture forbids it, this is a theological argument: if we prove it from the laws of the land, it is political ; but if we prove it from the principles of reason and equity, the argument is moral.
II. Arguments are either certain and evident, or doubtful and merely probable.
Probable arguments are those whose conclusions are proved by some probable medium ; as, this hill was once a church-yard, or a field of battle, because there are many human bones found here. This is not a certain argument, for human bones might have been conveyed there some other way.
Evident and certain arguments are called demonstrations ; for they prove their conclusions by clear mediums and undoubted principles; and they are generally divided into these two sorts :
1. Demonstrations a priori, which prove the effect by its necessary cause; as, I prove the scripture is ille fallibly true ; because it is the word of God, who cannot lie.
2. Demonstrations a posteriori, which infer the cause from its necessary effects; as, I infer their hath been the hand of some artificer here, because I find a curious engine. Or, I infer, there is a God, from the works of his wisdom in the vifible world.
The last of these is called " demonstratio tou oti," becauie it proves only the existence of a thing; the firib
IIL named “ demonstratia tou diote,” because it fhews also the cause of existence.
But note, that though these two sorts of arguments are most peculiarly called demonstrations, yet general. ly any ítrong and convincing argument obtains that name; and it is the custom of mathematicians to call all their arguments demonstrations, from what medium soever they derive them.
III. Arguments are divided into artificial and inartificial.
An artificial argument is taken from the nature and circumstances of the things, and if the argument be strong, it produces a natural certainty; as, the world was at firit created by God, because nothing can create itself.
An inartificial argument is the testimony of another, and this is called original, when our information proceeds immediately from the persons concerned, or from eye or ear witnesses of the fact : it is called tradition when it is delivered by the report of others.
We have taken notice before, that testimony is either divine or human. If the human testimony be strong, it produces a moral certainty ; but divine testimony produces a fupernatural certainty, which is far superior.
Note, Arguments taken from human testimony, as well as from laws and rules of equity, are called moral; and indeed the same name is also applied to every fort of argument which is drawn from the free actions of God, or the contingent actions of men, wherein we cannot arise at a natural certainty, but content ourselves with an high degree of probability, which in many cases is scarce inferior to natural certainty.
IV. Arguments are either direct or indirect. It is a direct argument where the middle term is such as proves the question itself, and infers that very propofi. tion which was the matter of inquiry. An indirect cs oblique argument proves, or refutes some other proposition, and thereby makes the thing inquired appear to be true by plain consequence.
Several arguments are called indire&t ; as, (1.) when some contradictory proposition is proved to be false, improbable or impoflible : or, when, upon supposition
of the falsehood, or denial of the original proposition, fome absurdity is inferred. This is called a proof per impossibile, or a reductio ad abfurdum. (2) When some other proposition is proved to be true which is less pro: bable, and thence it follows, that the original proposition is true ; because it is more probable. This is an argument ex magis probabili ad minus. (3.) When any other proposition is proved upon which it was before agreed to yield the original question. This is an are gument ex concejo.
V. There is yet another rank of arguments which have Latin names ; their true distinction is derived from the topics or middle terms which are used in them, though they are called an address to our judge ment, our faith, our ignorance, our profeflion, our nodesty, or our passions.
1. If an argument be taken from the nature or exist. ence of things, and addressed to the reason of mankind, it is called argumentum ad judicium.
2. When it is borrowed from some convincing testimony, it is called argumentum ad fidem, an address to our faith.
3. When it is drawn from any insufficient medium whatsoever, and yet the opposer has not skill to refute or answer it, this is argumentum ad ignorantiam, an address to our ignorance.
4. When it is built upon the professed principles or opinions of the person with whom we argue, whether the opinions be true or false, it is named argumentum ad hominem, an address to our profeffed principles. St Paul often uses this argument when he reasons with the Jews, and when he says I speak as a man..
5. When the argument is fetched from the sentiments of some wise, great, or good men, whose authority we reverence and hardly dare oppose, it is called argumentum ad verecundiam, an address to our modesty. .6. I add finally, when an argument is borrowed from any topics which are suited to engage the inclinations and passions of the hearers on the side of the fpeaker, rather than to convince the judgment, this is Argumentum ad pafiones, an address to the passions ; or
if it be made publicly, it is called ad populum, or an appeal to the people. . in i
After all these divisions of syllogism or argument arising from the middle term, there is one distinction proper to be mentioned which arises from the premises. An argument is called uniform when both the premises are derived from the same spring of knowledge, whether it be sense, reason, conscioufness, human, faith, or divine faith: But when the two premises are derived from different springs of knowledge, it is called a mixt argument.
Whether the conclusion must be called human or divine, when one or both premises are matters of dia vine faith, but the conclufion is drawn by human reafon, I leave to be disputed and determined in the schools of theology. .
Thus the second chapter is finished, and a particufar account given of all the chief kinds of syllogisms of arguments which are made use of among men, or treated of in logic, together with special rules for the formation of them, as far as is necessary. . .
If a syllogism agree with the rules which are given for the construction and regulation of it, it is called a true argument: If it disagree with these rules, it is a paralogism, or false argument: but when a false argue ment puts on the face and appearance of a true one, then it is properly called a sophism or fallacy, which Thall be the subject of the next chapter.
QROM truth nothing can really follow but what t is true; whensoever therefore we find a false conclusion drawn from premises which seem to be true, there must be some fault in the deduction or inference: or else one of the premises is not true in the sense in which it is used in that argument.