This proportion is called by the mathematicians a geometrical proportion; for it is when four terms are in geometrical proportion that the sum [of the first and third] is to the sum [of the second and fourth] in the original ratio [of the first to the second or the third to the fourth].

But this proportion [as applied in justice] cannot be a continuous proportion; for one term cannot represent both a person and a thing.

That which is just, then, in this sense is that which is proportionate; but that which is unjust is that which is disproportionate. In the latter case one quantity becomes more or too much, the other less or too little. And this we see in practice; for he who wrongs another gets too much, and he who is wronged gets too little of the good in question: but of the evil conversely; for the lesser evil stands in the place of good when compared with the greater evil: for the lesser evil is more desirable than the greater, but that which is desirable is good, and that which is more desirable is a greater good.