It is a sort of statement like this:—"If on the day on which that murder was committed at Rome, I was at Athens, I could not have been present at that murder." Because this is manifestly true, there is no need to adduce proof of it; wherefore, it is proper at once to assume the fact, in this way:—"But I was at Athens on that day." If this is not notorious, it requires proof; and when the proof is furnished the conclusion must follow:—"Therefore I could not have been present at the murder." There is, therefore, a certain kind of proposition which does not require proof. For why need one waste time in proving that there is a kind which does require proof; for that is easily visible to all men. And if this be the case, from this fact, and from that statement which we have established, it follows that proof is something distinct from a proposition. And if it is so, it is evidently false that argumentation is susceptible of only three divisions.
In the same manner it is plain that there is another sort of proof also which is distinct from assumption. For if in some sort of argumentation it is sufficient to use assumption, and if it is not requisite to add proof to the assumption; and if, again, in some sort of argumentation assumption is invalid unless proof be added to it; then proof is something separate and distinct from assumption. But there is a kind of argumentation in which assumption does not require proof; and a certain other kind in which it is of no use without proof; as we shall show. Proof, then, is a thing distinct from assumption. And we will demonstrate that which we have promised to in this manner.
That assumption which contains a truth evident to all men has no need of proof. That is an assumption of this sort:—"If it be desirable to be wise, it is proper to pay attention to philosophy." This proposition requires proof. For it is not self-evident. Nor is it notorious to all men, because many think that philosophy is of no service at all, and some think that it is even a disservice. A self-evident assumption is such as this:—"But it is desirable to be wise." And because this is of itself evident from the simple fact, and is at once perceived to be true, there is no need that it be proved. Wherefore, the argumentation may be at once terminated:—"Therefore it is proper to pay attention to philosophy." There is, therefore, a certain kind of assumption which does not stand in need of proof; for it is evident that is a kind which does. Therefore, it is false that argumentation is susceptible of only a threefold division.
XXXVII. And from these considerations that also is evident, that there is a certain kind of argumentation in which neither proposition nor assumption stands in need of proof, of this sort, that we may adduce something undoubted and concise, for the sake of example. "If wisdom is above all things to be desired, then folly is above all things to be avoided; but wisdom is to be desired above all things, therefore folly is above all things to be avoided." Here both the assumption and the proposition are self-evident, on which account neither of them stands in need of proof. And from all these facts it is manifest that proof is at times added, and at times is not added. From which it is palpable that proof is not contained in a proposition, nor in an assumption, but that each being placed in its proper place, has its own peculiar force fixed and belonging to itself. And if that is the case, then those men have made a convenient arrangement who have divided argumentation into five parts.
Are there five parts of that argumentation which is carried on by ratiocination? First of all, proposition, by which that topic is briefly explained from which all the force of the ratiocination ought to proceed. Then the proof of the proposition, by which that which has been briefly set forth being corroborated by reasons, is made more probable and evident. Then assumption, by which that is assumed which, proceeding from the proposition, has its effect on proving the case. Then the proof of the assumption, by which that which has been assumed is confirmed by reasons. Lastly, the summing up, in which that which results from the entire argumentation is briefly explained. So the argumentation which has the greatest number of divisions consists of these five parts.
The second sort of argumentation has four divisions; the third has three. Then there is one which has two; which, however, is a disputed point. And about each separate division it is possible that some people may think that there is room for a discussion.
XXXVIII. Let us then bring forward some examples of those matters which are agreed upon. And in favour of those which are doubtful, let us bring forward some reasons. Now the argumentation which is divided into five divisions is of this sort:—It is desirable, O judges, to refer all laws to the advantage of the republic, and to interpret them with reference to the general advantage, and according to the strict wording according to which they are drawn up. For our ancestors were men of such virtue and such wisdom, that when they were drawing up laws, they proposed to themselves no other object than the safety and advantage of the republic; for they were neither willing themselves to draw up any law which could be injurious; and if they had drawn up one of such a character, they were sure that it would be rejected when its tendency was perceived. For no one wishes to preserve the laws for the sake of the laws, but for the sake of the republic; because all men believe that the republic is best managed by means of laws. It is desirable, therefore, to interpret all written laws with reference to that cause for the sake of which it is desirable that the laws should be preserved. That is to say, since we are servants of the republic, let us interpret the laws with reference to the advantage and benefit of the republic. For as it is not right to think that anything results from medicine except what has reference to the advantage of the body, since it is for the sake of the body that the science of medicine has been established; so it is desirable to think that nothing proceeds from the laws except what is for the advantage of the republic, since it is for the sake of the republic that laws were instituted.
Therefore, while deciding on this point, cease to inquire about the strict letter of the law, and consider the law (as it is reasonable to do) with reference to the advantage of the republic. For what was more advantageous for the Thebans than for the Lacedaemonians to be put down? What object was Epaminondas, the Theban general, more bound to aim at than the victory of the Thebans? What had he any right to consider more precious or more dear to him, than the great glory then acquired by the Thebans, than such an illustrious and magnificent trophy? Surely, disregarding the letter of the law, it became him to consider the intention of the framer of the law. And this now has been sufficiently insisted on, namely, that no law has ever been drawn up by any one, that had not for its object the benefit of the commonwealth. He then thought that it was the very extremity of madness, not to interpret with reference to the advantage of the republic, that which had been framed for the sake of the safety of the republic. And it is right to interpret all laws with reference to the safety of the republic; and if he was a great instrument of the safety of the republic, certainly it is quite impossible that he by one and the same action should have consulted the general welfare, and yet should have violated the laws.
XXXIX. But argumentation consists of four parts, when we either advance a proposition, or claim an assumption without proof. That it is proper to do when either the proposition is understood by its own merits, or when the assumption is self-evident and is in need of no proof. If we pass over the proof of the proposition, the argumentation then consists of four parts, and is conducted in this manner:—"O judges, you who are deciding on your oaths, in accordance with the law, ought to obey the laws; but you cannot obey the laws unless you follow that which is written in the law. For what more certain evidence of his intention could the framer of a law leave behind him, than that which he himself wrote with great care and diligence? But if there were no written documents, then we should be very anxious for them, in order that the intention of the framer of the law might be ascertained; nor should we permit Epaminondas, not even if he were beyond the power of this tribunal, to interpret to us the meaning of the law; much less will we now permit him, when, the law is at hand, to interpret the intention of the lawgiver, not from that which is most clearly written, but from that which is convenient for his own cause. But if you, O judges, are bound to obey the laws, and if you are unable to do so unless you follow what is written in the law; what can hinder your deciding that he has acted contrary to the laws?"
But if we pass over the proof of the assumption, again the argumentation will be arranged under four heads, in this manner:—"When men have repeatedly deceived us, having pledged their faith to us, we ought not to give credit to anything that they say for if we receive any injury; in consequence of their perfidy, there will be no one except ourselves whom we shall have any right to accuse. And in the first place, it is inconvenient to be deceived, in the next place, it is foolish, thirdly, it is disgraceful. But the Carthaginians have before this deceived us over and over again. It is therefore the greatest insanity to rest any hopes on their good faith, when you have been so often deceived by their treachery."