The figure of a syllogism what it is.
7. Syllogisms are usually distinguished according to their diversity of figures, that is, by the diverse position of the middle term. And again in figure there is a distinction of certain moods, which consist of the differences of propositions in quantity and quality. The first figure is that, in which the terms are placed one after another according to their latitude of signification; in which order the minor term is first, the middle term next, and the major last; as, if the minor term be man, the middle term, living creature, and the major term, body, then, man is a living-creature, is a body, will be a syllogism in the first figure: in which, man is a living creature is the minor proposition; the major, living creature is a body, and the conclusion, or sum of both, man is a body. Now this figure is called direct, because the terms stand in direct order; and it is varied by quantity and quality into four moods: of which the first is that wherein all the terms are positive, and the minor term universal, as every man is a living creature, every living creature is a body: in which all the propositions are affirmative, and universal. But if the major term be a negative name, and the minor an universal name, the figure will be in the second mood, as, every man is a living creature, every living creature is not a tree, in which the major proposition and conclusion are both universal and negative. To these two, are commonly added two more, by making the minor term particular. Also it may happen that both the major and middle terms are negative terms, and then there arises another mood, in which all the propositions are negative, and yet the syllogism will be good; as, if the minor term be man, the middle term not a stone, and the major term not a flint, this syllogism, no man is a stone, whatsoever is not a stone is not a flint, therefore, no man is a flint, is true, though it consist of three negatives. But in philosophy, the profession whereof is to establish universal rules concerning the properties of things, seeing the difference betwixt negatives and affirmatives is only this, that in the former the subject is affirmed by a negative name, and by a positive in the latter, it is superfluous to consider any other mood in direct figure, besides that, in which all the propositions are both universal and affirmative.
What is in the mind answering to a syllogism.
8. The thoughts in the mind answering to a direct syllogism, proceed in this manner; first, there is conceived a phantasm of the thing named, with that accident or quality thereof, for which it is in the minor proposition called by that name which is the subject; next, the mind has a phantasm of the same thing with that accident, or quality, for which it hath the name, that in the same proposition is the predicate; thirdly, the thought returns of the same thing as having that accident in it, for which it is called by the name, that is the predicate of the major proposition; and lastly, remembering that all those are the accidents of one and the same thing, it concludes that those three names are also names of one and the same thing; that is to say, the conclusion is true. For example, when this syllogism is made, man is a living creature, a living creature is a body, therefore, man is a body, the mind conceives first an image of a man speaking or discoursing, and remembers that that, which so appears, is called man; then it has the image of the same man moving, and remembers that that, which appears so, is called living creature; thirdly, it conceives an image of the same man, as filling some place or space, and remembers that what appears so is called body; and lastly, when it remembers that that thing, which was extended, and moved and spake, was one and the same thing, it concludes that the three names, man, living creature, and body, are names of the same thing, and that therefore man is a living creature is a true proposition. From whence it is manifest, that living creatures that have not the use of speech, have no conception or thought in the mind, answering to a syllogism made of universal propositions; seeing it is necessary to think not only of the thing, but also by turns to remember the divers names, which for divers considerations thereof are applied to the same.
The first indirect figure how made.
9. The rest of the figures arise either from the inflexion, or inversion of the first or direct figure; which is done by changing the major, or minor, or both the propositions, into converted propositions equipollent to them.
From whence follow three other figures; of which, two are inflected, and the third inverted. The first of these three is made by the conversion of the major proposition. For let the minor, middle, and major terms stand in direct order, thus, man is a living creature, is not a stone, which is the first or direct figure; the inflection will be by converting the major proposition in this manner, man is a living creature, a stone is not a living creature; and this is the second figure, or the first of the indirect figures; in which the conclusion will be, man is not a stone. For (having shown in the last chapter, [art. 14], that universal propositions, converted by contradiction of the terms, are equipollent) both those syllogisms conclude alike; so that if the major be read (like Hebrew) backwards, thus, a living creature is not a stone, it will be direct again, as it was before. In like manner this direct syllogism, man is not a tree, is not a pear-tree, will be made indirect by converting the major proposition (by contradiction of the terms) into another equipollent to it, thus, man is not a tree, a pear-tree is a tree; for the same conclusion will follow, man is not a pear-tree.
But for the conversion of the direct figure into the first indirect figure, the major term in the direct figure ought to be negative. For though this direct, man is a living creature, is a body, be made indirect, by converting the major proposition, thus,
Man is a living creature,
Not a body is not a living creature,