defined. Whatever is affirmed or denied of the genus, may be affirmed or denied of the fpecies, &c.

Metaphyfical canons are fuch as thefe; final causes belong only to intelligent agents. If a natural and neceffary caule operate, the effect will follow, &c. and there are large catalogues of many more in each distinct fcience.

Now it has been the custom of those who teach logic or rhetoric, to direct their difciples, when they want an argument, to confult the feveral topics which are fuited to their 1ubject of difcourfe, and to 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 folemnity in fome Ichools.

I grant there may be good ufe of this practice for perfons of a lower genius, when they are to compofe any difcourfe for the public; or for those of superior parts to refresh their memory, and revive their acquaintance with a fubject which has been long abfent from their thoughts, or when their natural spirits labour under indifpofition and langour; but when a man of moderate fagacity has made himself master of his theme by juft diligence and inquiry, he has feldom need to run knocking at the doors of all the topics, that he may furnith himfelf with argument or matter of speaking; and indeed it is only a man of fense 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 fome logical writers this bufinefs of topics and invention is treated of in fuch a manner with mathemati cal figures and diagrams, filled with the barbarous technical words, Napcas, Nipcis, Ropcos, Nofrop, &c. as though an ignorant lad were to be led mechanically in certain artifical harneffes and trammels to find out arguments to prove or refute any propofition whatsoever, without any rational knowledge of the ideas. Now there is no need to throw words of contempt on fuch a practice; the very defcription of it carries reproof and. ridicule in abundance.

SECT. VIII.

Of feveral Kinds of Arguments and Demonftrations.

WE

proceed now to the divifion of fyllogifms according to the middle term; and in this part of our treatise the fyllogifms themselves are properly called arguments, and are thus diftributed.

I. Arguments are called Grammatical, Logical, Metaphyfical, Phyfical, Moral, Mechanical, Theological, &c. according to the art, fcience or fubject, whence the middle term or topic is borrowed. Thus if we prove that no man fhould fteal from his neighbour becaufe the fcripture 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 reafon and equity, the argument is moral.

II. Arguments are either certain and evident, or doubtful and merely probable.

Probable arguments are thofe whose conclufions are proved by fome 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 fome other way.

Evident and certain arguments are called demonftrations; for they prove their conclufions by clear mediums and undoubted principles; and they are generally divided into these two forts:

1. Demonftrations a priori, which prove the effect by its neceffary caufe; as, I prove the fcripture is infallibly true; because it is the word of God, who cannot lie.

2. Demonftrations a pofteriori, which infer the caufe from its neceffary effects; as, I infer their hath been the hand of fome artificer here, because I find a curious engine. Or, I infer, there is a God, from the works of his wifdom in the vifible world.

The laft of thefe is called "demonftratio tou oti," becaule it proves only the existence of a thing; the firit

named "demonftratio tou diote," because it fhews alfo the cause of existence,

But note, that though thefe two forts of arguments are most peculiarly called demonftrations, yet generally any strong and convincing argument obtains that name; and it is the custom of mathematicians to call all their arguments demonftrations, from what medium foever they derive them.

III. Arguments are divided into artificial and inarti

ficial.

An artificial argument is taken from the nature and circumftances of the things; and if the argument be strong, it produces a natural certainty; as, the world was at firft created by God, because nothing can create itself.

An inartificial argument is the teftimony of another, and this is called original, when our information proceeds immediately from the perfons concerned, or from eye or ear witneffes of the fact it is called tradition when it is delivered by the report of others.

We have taken notice before, that teftimony is either divine or human. If the human teftimony be strong, it produces a moral certainty; but divine teftimony produces a fupernatural certainty, which is far fuperior.

Note, Arguments taken from human teftimony, as well as from laws and rules of equity, are called moral; and indeed the fame name is alfo 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 ourfelves with an high degree of probability, which in many cafes is fcarce 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 propofition which was the matter of inquiry. An indirect or oblique argument proves, or refutes fome other propofition, and thereby makes the thing inquired appear to be true by plain confequence.

Several arguments are called indirect; as, (1) when fome contradictory propofition is proved to be falfe, improbable or impoffible: or, when, upon fuppofition

of the falsehood, or denial of the original proposition, fome abfurdity is inferred. This is called a proof per impoffibile, or a reductio ad abfurdum. (2) When fome other propofition is proved to be true which is lefs probable, 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 propofition is proved upon which it was before agreed to yield the original queftion. This is an argument ex conceffo.

V. There is yet another rank of arguments which have Latin names; their true diftinction is derived from the topics or middle terms which are used in them, though they are called an addrefs to our judgment, our faith, our ignorance, our profeffion, our modefty, or our paffions.

1. If an argument be taken from the nature or exiftence of things, and addreffed to the reason of mankind, it is called argumentum ad judicium.

2. When it is borrowed from fome convincing teftimony, it is called argumentum ad fidem, an address to our faith.

3. When it is drawn from any infufficient medium whatfoever, and yet the oppofer has not skill to refute or answer it, this is argumentum ad ignorantiam, an addrefs to our ignorance.

4. When it is built upon the profeffed principles or opinions of the perfon with whom we argue, whether the opinions be true or falfe, it is named argumentum ad hominem, an addrefs to our profeffed principles. St Paul often uses this argument when he reafons with the Jews, and when he fays I fpeak as a man.

5. When the argument is fetched from the fentiments of fome wife, great, or good men, whose authority we reverence and hardly dare oppose, it is called argumentum ad verecundiam, an addrefs to our modefty.

6. I add finally, when an argument is borrowed from any topics which are fuited to engage the inclinations and paffions of the hearers on the fide of the Speaker, rather than to convince the judgment, this is argumentum ad paffiones, an addrefs to the paffions; or

if it be made publicly, it is called ad populum, or an appeal to the people.

After all thefe divifions of fyllogifm or argument arifing from the middle term, there is one diftinction proper to be mentioned which arifes from the premises. An argument is called uniform when both the premises are derived from the fame fpring of knowledge, whe ther it be fenfe, reason, confcioufnefs, human, faith, or divine faith: But when the two premifes are derived from different fprings of knowledge, it is called a mixt argument.

Whether the conclufion must be called human or divine, when one or both premifes are matters of divine faith, but the conclufion is drawn by human reafon, I leave to be difputed and determined in the fchools of theology.

Thus the fecond chapter is finished, and a particular account given of all the chief kinds of fyllogifms or arguments which are made ufe of among men, or treated of in logic, together with fpecial rules for the formation of them, as far as is neceffary.

If a fyllogifm agree with the rules which are given for the conftruction and regulation of it, it is called a true argument: If it difagree with thefe rules, it is a paralogifm, or falfe argument: but when a falte argument puts on the face and appearance of a true one, then it is properly called a fophifm or fallacy, which fhall be the fubject of the next chapter.

FRO

CHAP. III.

The Doctrine of Syllogifms.

ROM truth nothing can really follow but what is true; whenfoever therefore we find a false conclufion drawn from premises which feem to be true, there must be fome fault in the deduction or inference: or else one of the premises is not true in the fenfe in which it is used in that argument.