recourse to the principles and science of defining.  And akin to this is that other argument also which we said was employed with respect to the subject in question and something else; and that is a species of definition.  For if the question is, “Whether pertinacity and perseverance are the same thing,” it must be decided by definitions.  And the topics which are incidental to a discussion of this kind are those drawn from consequents, or antecedents, or inconsistencies, with the addition also of those two topics which are deduced from causes and effects.  For if such and such a thing is a consequence of this, but not a consequence of that; or if such and such a thing is a necessary antecedent to this, but not to that; or if it is inconsistent with this, but not with that; or if one thing is the cause of this, and another the cause of that; or if this is effected by one thing, and that by another thing; from any one of these topics it may be discovered whether the thing which is the subject of discussion is the same thing or something else.

With respect to the third kind of inquiry, in which the question is what the character of the matter in question is, those things are incidental to the comparison which were enumerated just now under the topic of comparison.  But in that kind of inquiry where the question is about what is to be sought for or avoided, those arguments are employed which refer to advantages or disadvantages, whether affecting the mind or body, or being external.  And again, when the inquiry is not what is honourable or discreditable, all our argument must be addressed to the good or bad qualities of the mind.

But when right and wrong are being discussed, all the topics of equity are collected.  These are divided in a two-fold manner, as to whether they are such by nature or owing to institutions.  Nature has two parts to perform, to defend itself, and to indicate right.  But the agreements which establish equity are of a threefold character:  one part is that which rests on laws; one depends on convenience; the third is founded on and established by antiquity of custom.  And again, equity itself is said to be of a threefold nature:  one division of it having reference to the gods above; another, to the shades below; a third, to mankind.  The first is called piety; the second, sanctity; the third, justice or equity.

XXIV.  I have said enough about propositions.  There are now a few things which require to be said about causes.  For they have many things in common with propositions.

There are then three kinds of causes; having for their respective objects, judgment, deliberation, and panegyric.  And the object of each points out what topics we ought to employ in each.  For the object of judicial judgment is right; from which also it derives its name.  And the divisions of right were explained when we explained the divisions of equity.  The object of deliberation is utility; of which the divisions have also been already explained when we were treating of things to be desired.  The object of panegyric is honour; concerning which also we have already spoken.