We may safely assert that the virtue (areté )or excellence of a thing causes that thing both to be itself in good condition and to perform its function well. The excellence of the eye, for instance, makes both the eye and its work good; for it is by the excellence of the eye that we see well. So the proper excellence of the horse makes a horse what it should be, and makes it good at running, and carrying his rider, and standing a charge.

If, then, this holds good in all cases, the proper excellence or virtue of man will be the habit or trained faculty that makes a man good and makes him perform his function well.

Now, if we have any quantity, whether continuous or discrete, it is possible to take either a larger (or too large), or a smaller (or too small), or an equal (or fair) amount, and that either absolutely or relatively to our own needs.

By an equal or fair amount I understand a mean amount, or one that lies between excess and deficiency.

By the absolute mean, or mean relative to the thing itself, I understand that which is equidistant from both extremes, and this is one and the same for all.

By the mean relative to us I understand that which is neither too much nor too little for us; and this is not one and the same for all.

For instance, if ten be too large, and two be too small, if we take six we take the mean relative to the thing itself [or the arithmetical mean]; for it exceeds one extreme by the same amount by which it is exceeded by the other extreme: and this is the mean in arithmetical proportion.

But the mean relative to us cannot be found in this way. If ten pounds of food is too much for a given man to eat, and two pounds too little, it does not follow that the trainer will order him six pounds: for that also may perhaps be too much for the man in question, or too little; too little for Milo, 1 too much for the beginner. The same holds true in running and wrestling.

And so we may say generally that a master in any art avoids what is too much and what is too little, and seeks for the mean and chooses it—not the absolute but the relative mean.

If, then, every art or science perfects its work in this way, looking into the mean and bringing its work up to this standard (so that people are accustomed to say of a good work that nothing could be taken from it or added to it, implying that excellence is destroyed by excess or deficiency, but secured by observing, the mean; and good artists, as we say, do in fact keep their eyes fixed on this in all that they do), and if virtue (areté), like nature, is more exact and better than any art, it follows that virtue also must aim at the mean—virtue of course meaning moral virtue or excellence, for it has to do with passions and actions, and it is these that admit of excess and deficiency and the mean. For instance, it is possible to feel fear, confidence, desire, anger, pity, and generally to be affected pleasantly and painfully, either too much or too little, in either case wrongly; but to be thus affected at the right times, and on the right occasions, and towards the right persons, and with the right object, and in the right fashion, is the mean course and the best course, and these are characteristics of virtue. And in the same way our outward acts also admit of excess and deficiency, and the mean or due amount. Virtue, then, has to deal with feelings or passions and with outward acts, in which excess is wrong and deficiency also is blamed, but the mean amount is praised and is right—both of which are characteristics of virtue.

Virtue, then, is a kind of moderation inasmuch as it aims at the mean or moderate amount.