Book 2: Moral Virtue.
There are, as we said, three classes of disposition, viz. two kinds of vice, one marked by excess, the other by deficiency, and one kind of virtue, the observance of the mean. Now, each is in a way opposed to each, for the extreme dispositions are opposed both to the mean or moderate disposition and to one another, while the moderate disposition is opposed to both the extremes. Just as a quantity which is equal to a given quantity is also greater when compared with a less, and less when compared with a greater quantity, so the mean or moderate dispositions exceed as compared with the defective dispositions, and fall short as compared with the excessive dispositions, both in feeling and in action; e.g. the courageous man seems foolhardy as compared with the coward, and cowardly as compared with the foolhardy; and similarly the temperate man appears profligate in comparison with the insensible, and insensible in comparison with the profligate man; and the liberal man appears prodigal by the side of the illiberal man, and illiberal by the side of the prodigal man.
And so the extreme characters try to displace the mean or moderate character, and each represents him as falling into the opposite extreme, the coward calling the courageous man foolhardy, the foolhardy calling him coward, and so on in other cases.
But while the mean and the extremes are thus opposed to one another, the extremes are strictly contrary to each other rather than to the mean; for they are further removed from one another than from the mean, as that which is greater than a given magnitude is further from that which is less, and that which is less is further from that which is greater, than either the greater or the less is from that which is equal to the given magnitude.
Sometimes, again, an extreme, when compared with the mean, has a sort of resemblance to it, as foolhardiness to courage, or prodigality to liberality; but there is the greatest possible dissimilarity between the extremes.
Again, “things that are as far as possible removed from each other” is the accepted definition of contraries, so that the further things are removed from each other the more contrary they are.
In comparison with the mean, however, it is sometimes the deficiency that is the more opposed, and sometimes the excess; e.g. foolhardiness, which is excess, is not so much opposed to courage as cowardice, which is deficiency; but insensibility, which is lack of feeling, is not so much opposed to temperance as profligacy, which is excess.
The reasons for this are two. One is the reason derived from the nature of the matter itself: since one extreme is, in fact, nearer and more similar to the mean, we naturally do not oppose it to the mean so strongly as the other; e.g. as foolhardiness seems more similar to courage and nearer to it, and cowardice more dissimilar, we speak of cowardice as the opposite rather than the other: for that which is further removed from the mean seems to be more opposed to it.
This, then, is one reason, derived from the nature of the thing itself. Another reason lies in ourselves: and it is this—those things to which we happen to be more prone by nature appear to be more opposed to the mean: e.g.our natural inclination is rather towards indulgence in pleasure, and so we more easily fall into profligate than into regular habits: those courses, then, in which we are more apt to run to great lengths are spoken of as more opposed to the mean; and thus profligacy, which is an excess, is more opposed to temperance than the deficiency is.