Chapter II. On Dialectical Syllogism.

CHAPTER II.

On dialectical syllogism.

But dialectical syllogism, after demonstration, participates in the account of syllogism, because it adds less over and above the consequence of syllogism and the necessity of the consequence than demonstration does: just as that which attains the cause through necessity is more truly a cause than that which attains the cause through probability. A dialectical syllogism is that which is from probable things as to matter, and is syllogized as to form, which comes from the number and order of terms in figure, and from mode, which is the combination of propositions according to the due form in quality and quantity and in the order of quality and quantity. And although a syllogism can be made from an affirmative and a negative, nevertheless the minor proposition in the first and third figure cannot be negative: and if it is made so, such a syllogism has not been syllogized, because it does not have the form of a useful combination. But what probable things are will be said below, and for its sake we shall first set down the declaration of those things that were said before in the definition of demonstration, saying that true and first things are those that have credibility not through other things as through middles or principles, but through themselves according to their own nature; and these are dignities that anyone approves when heard. For just as in sight certain alien things are manifested by light, such as colored things, while certain things are manifested by their own light, as luminous things are: so it is in intellectual matters, that first things, not having a middle of their constitution between the light of intelligence and themselves, but constituted by the intellectual light itself, are manifested to intellect by their own light. But other things that proceed through mediating forms of other things are constituted by intelligence and are not received by intellect unless they are illuminated by the light of the first things: and those that are received in this way are second and not first, because they are not immediately joined to the light of intelligence.

No intelligible is received by the intelligence of a human being except insofar as it is the light of the intelligence acting upon it; and if that intelligence acts alone, it is understood through itself; but if it acts upon it through a middle, it must be illuminated by the light of that intelligence before it is received by the intellect. But what is the cause on account of which certain things are understood through themselves has now been said.

And from this it is further caused that one must not seek, that is, one must not seek in disciplinary or doctrinal sciences by seeking why: for in disciplinary or doctrinal sciences one proceeds from first, true, and immediate things, that is, things for syllogizing which there is no middle; and therefore in them one must not seek why, because the term saying why is the middle, as Aristotle says; and since such things do not have a middle, why is not sought; because if they had a term why, they would have a middle, and so they would not be immediate. But each thing that belongs to the first principles must itself be credibility to itself, that is, a cause of belief. For belief is the assent of the respondent into it, as has been said; on account of which such first principles are called common conceptions of the soul, as Avicenna says, because the soul of the hearer immediately assents to them; on account of which such things are also called indemonstrable. Therefore these are the principles of demonstration, from which demonstrative syllogism is made.

But probable things, from which dialectical syllogism is made, are truth-like things. Now truth-like things are twofold: for either they are truth-like in themselves, because the very relation of predicate to subject is truth-like, since neither is the predicate in the subject per se, nor the subject in the predicate per se, nor each in the other, nor does the predicate have a necessary and essential inherence with the subject, but the truth-like is accepted in signs, not in necessary causes. Or they are so because it has necessary inherence, but is accepted only through a sign: and this is probable according to the mode of acceptance, although in itself it is necessary; as that the sun is larger than the earth, because everywhere it appears of one quantity, is accepted probably ¹. But that the sun is larger than the earth, accepted through the quantity of diameter, is necessary and not probable, according as the probable and the necessary are opposed. But the probable, so called truth-like, is what, through the figure of its own truth, seems so to all or to many or to the wise; and to these wise persons it seems so to all or to many or to the most noted and probable: so that for wise persons and these, whether all wise persons or many or the most noted or probable, the whole is placed for one member.

But signs of truth-likeness either occur immediately on the surface and in the exteriors of the thing, which the sensitive power receives by comparing sensed things to one another; and if the signs are such, the probable is what seems so to all, as that snow is white because snow is small parts of something transparent joined in smallness, in whose parts light is poured out from every side: for this sign is the middle for sense. But if signs making an indication about truth-likeness are not on the surface, but are in some way deepened, not to necessary things, yet not remaining outwardly on the surface, then there is what seems so to many: because they mix something of reason with sense, as that the star in the tail of the Little Bear is the pole, because its singular motion is not detected; for this judgment of reason is mixed with sense. But if the sign of truth-likeness is deepened into the causes of essential and convertible things that are convertible as causes, then there is what seems so to the wise, as that the moon is moved in an epicycle, because it passes more deeply and higher through the shadow of the earth: for this is not a cause but a sign.

Therefore that which seems so to the wise has degrees, because either it seems so to all, or to many, or to the most noted or probable. Because a sign convertible with a cause either appears mixed with sense, and then it seems so to all; or it is deepened in the very substantial things, and then it does not seem so except to approved and probable wise persons; or it is accepted in a middle way, and this in two ways. For if it is more inclined toward sense, then it seems so to many wise persons. But if it is more deepened toward necessary essential and intellectual things, then it is what seems so to the most noted, who have known how to detect this from the power of science and art. Therefore this is the probable, from which dialectical syllogism is made, namely what is detected by a sign such and diversified in such a way. This is the meaning of the Arabic commentary: and thus the science of demonstrative syllogisms and also of dialectical syllogisms has been determined.