XIII. The next topic is one peculiar to dialecticians; derived from consequents, and antecedents, and inconsistencies; and this one is very different from that drawn from differences. For adjuncts, of which we were speaking just now, do not always exist, but consequents do invariably. I call those things consequents which follow an action of necessity. And the same rule holds as to antecedents and inconsistencies; for whatever precedes each thing, that of necessity coheres with that theme; and whatever is inconsistent with it is of such a nature that it can never cohere with it. As then this topic is distributed in three divisions, into consequence, antecession, and inconsistency, there is one single topic to help us find the argument, but a threefold way of dealing with it. For what difference does it make, when you have once assumed that the ready money is due to the woman to whom all the money has been bequeathed, whether you conclude your argument in this way:—"If coined money is money, it has been bequeathed to the woman; but coined money is money; therefore it has been bequeathed to her;"—or in this way: "If ready money has not been bequeathed to her, then ready money is not money; but ready money is money; therefore it has been bequeathed to her;"—or in this way: "The cases of money not having been bequeathed, and of ready money not having been bequeathed, are identical; but money was bequeathed to her; therefore ready money was bequeathed to her?" But the dialecticians call that conclusion of the argument in which, when you have first made an assumption, that which is connected with it follows as a consequence of the assumption, the first mood of the conclusion; and when, because you have denied the consequence, it follows that that also to which it was a consequence must be denied also, that is the second mood. But when you deny some things in combination, (and then another negation is added to them,) and from these things you assume something, so that what remains is also done away with, that is called the third mood of the conclusion. From this are derived those results of the rhetoricians drawn from contraries, which they call enthymemes. Not that every sentence may not be legitimately called an enthymeme; but, as Homer on account of his preeminence has appropriated the general name of poet to himself as his own among all the Greeks; so, though every sentence is an enthymeme, still, because that which is made up of contraries appears the most acute argument of the kind, that alone has possessed itself of the general name as its own peculiar distinction. Its kinds are these:—"Can you fear this man, and not fear that one?"—"You condemn this woman, against whom you bring no accusation; and do you say that this other one deserves punishment, whom you believe to deserve reward?"—"That which you do know is no good; that which you do not know is a great hindrance to you."
XIV. This kind of disputing is very closely connected with the mode of discussion adopted by you lawyers in reply, and still more closely with that adopted by philosophers, as they share with the orators in the employment of that general conclusion which is drawn from inconsistent sentences, which is called by dialecticians the third mood, and by rhetoricians an enthymeme. There are many other moods used by the rhetoricians, which consist of disjunctive propositions:—"Either this or that is the case; but this is the case; then that is not the case." And again:—"Either this or that is the case; but this is not the case; then that is the case." And these conclusions are valid, because in a disjunctive proposition only one alternative can be true. And from those conclusions which I have mentioned above, the former is called by the dialecticians the fourth mood, and the latter the fifth. Then they add a negation of conjunctive propositions; as, "It is not both this and that; but it is this; therefore it is not that." This is the sixth mood. The seventh is, "It is not both this and that; but it is not this; therefore it is that." From these moods innumerable conclusions are derived, in which nearly the whole science of dialectics consists. But even those which I have now explained are not necessary for this present discussion.
XV. The next topic is drawn from efficient circumstances which are called causes; and the next from the results produced by these efficient causes. I have already given instances of these, as of the other topics, and those too drawn from civil law; but these have a wider application.
There are then two kinds of causes; one which of its own force to a certainty produces that effect which is subordinate to it; as, "Fire burns;" the other is that which has no nature able to produce the effect in question, though still that effect cannot be produced without it; as, if any one were to say, that "brass was the cause of a statue; because a statue cannot be made without it." Now of this kind of causes which are indispensable to a thing being done, some are quiet some passive, some, as it were, senseless; as, place, time, materials, tools, and other things of the same sort. But some exhibit a sort of preparatory process towards the production of the effect spoken of; and some of themselves do contribute some aid to it; although it is not indispensable; as meeting may have supplied the cause to love; love to crime. From this description of causes depending on one another in infinite series, is derived the doctrine of fate insisted on by the Stoics. And as I have thus divided the genera of causes, without which nothing can be effected, so also the genera of the efficient causes can be divided in the same manner. For there are some causes which manifestly produce the effect, without any assistance from any quarter; others which require external aid; as for instance, wisdom alone by herself makes men wise; but whether she is able alone to make men happy is a question.
XVI. Wherefore, when any cause efficient as to some particular end has inevitably presented itself in a discussion, it is allowable without any hesitation to conclude that what that cause must inevitably effect is effected. But when the cause is of such a nature that it does not inevitably effect the result, then the conclusion which follows is not inevitable And that description of causes which has an inevitable effect does not usually engender mistakes; but this description, without which a thing cannot take place, does often cause perplexity. For it does not follow, because sons cannot exist without parents, that there was therefore any unavoidable cause in the parents to have children. This, therefore, without which an effect cannot be produced, must be carefully separated from that by which it is certainly produced. For that is like—
"Would that the lofty pine on Pelion's brow
Had never fall'n beneath the woodman's axe!"
For if the beam of fir had never fallen to the ground, that Argo would not have been built; and yet there was not in the beams any unavoidably efficient power. But when
"The fork'd and fiery bolt of Jove"
was hurled at Ajax's vessel, that ship was then inevitably burnt.
And again, there is a difference between causes, because some are such that without any particular eagerness of mind, without any expressed desire or opinion, they effect what is, as it were, their own work; as for instance, "that everything must die which has been born." But other results are effected either by some desire or agitation of mind, or by habit, or nature, or art, or chance. By desire, as in your case, when you read this book; by agitation, as in the case of any one who fears the ultimate issue of the present crisis; by habit, as in the case of a man who gets easily and rapidly in a passion; by nature, as vice increases every day; by art, as in the case of a man who paints well; by chance, as in the case of a man who has a prosperous voyage. None of these things are without some cause, and yet none of them are wholly owing to any single cause. But causes of this kind are not necessary ones.