XVIII.  Conjoined to this topic of causes is that topic which is supplied by causes.  For as cause indicates effect, so what has been effected points out what the efficient cause has been.  This topic ordinarily supplies to orators and poets, and often to philosophers also, that is to say, to those who have an elegant and argumentative and rich style of eloquence, a wonderful store of arguments, when they predict what will result from each circumstance.  For the knowledge of causes produces a knowledge of effects.

The remaining topic is that of comparison, the genus and instances of which have been already explained, as they have in the case of the other topics.  At present we must explain the manner of dealing with this one.  Those things then are compared which are greater than one another, or less than one another, or equal to one another.  In which these points are regarded; number, appearance, power, and some particular relation to some particular thing.

Things will be compared in number thus:  so that more advantages may be preferred to fewer; fewer evils to more; more lasting advantages to those which are more short-lived; those which have an extensive application to those the effect of which is narrowed:  those from which still further advantages may be derived, and those which many people may imitate and reproduce.

Things again will be compared with reference to their appearance, so that those things may be preferred which are to be desired for their own sake, to those which are only sought for the sake of something else:  and so that innate and inherent advantages may be preferred to acquired and adventitious ones; complete good to mixed good; pleasant things to things less pleasant; honourable things to such as are merely useful; easy things to difficult ones; necessary to unnecessary things; one’s own advantage to that of others; rare things to common ones; desirable things to those which you can easily do without; things complete to things which are only begun; wholes to parts; things proceeding on reason to things void of reason; voluntary to necessary things; animate to inanimate things; things natural to things not natural; things skilfully produced by art to things with which art has no connexion.

But power in a comparison is perceived in this way:  an efficient cause is more important than one which effects nothing; those causes which can act by themselves are superior to those which stand in need of the aid of others; those which are in our power are preferable to those which are in the power of another; lasting causes surpass those which are uncertain; things of which no one can deprive us are better than things which can be easily taken away.

But the way in which people or things are disposed towards some things is of this sort:  the interests of the chief citizens are more important than those of the rest:  and also, those things which are more agreeable, which are approved of by more people, or which are praised by the most virtuous men, are preferable.  And as in a comparison these things are the better, so those which are contrary to them are the worse.