The Just, then, is a certain proportionable thing. For proportion does
not apply merely to number in the abstract,[10] but to number
generally, since it is equality of ratios, and implies four terms at
least (that this is the case in what may be called discrete proportion
is plain and obvious, but it is true also in continual proportion, for
this uses the one term as two, and mentions it twice; thus A:B:C may be
expressed A:B::B:C. In the first, B is named twice; and so, if, as in
the second, B is actually written twice, the proportionals will be
four): and the Just likewise implies four terms at the least, and the
ratio between the two pair of terms is the same, because the persons
and the things are divided similarly. It will stand then thus,
A:B::C:D, and then permutando A:C::B:D, and then (supposing C and D to
represent the things) A+C:B+D::A:B. The distribution in fact consisting
in putting together these terms thus: and if they are put together so
as to preserve this same ratio, the distribution puts them together
justly.[11] So then the joining together of the first and third and
second and fourth proportionals is the Just in the distribution, and
this Just is the mean relatively to that which violates the
proportionate, for the proportionate is a mean and the Just is
proportionate. Now mathematicians call this kind of proportion
geometrical: for in geometrical proportion the whole is to the whole as
each part to each part. Furthermore this proportion is not continual,
because the person and thing do not make up one term.
The Just then is this proportionate, and the Unjust that which violates
the proportionate; and so there comes to be the greater and the less:
which in fact is the case in actual transactions, because he who acts
unjustly has the greater share and he who is treated unjustly has the
less of what is good: but in the case of what is bad this is reversed:
for the less evil compared with the greater comes to be reckoned for
good, because the less evil is more choice-worthy than the greater, and
what is choice-worthy is good, and the more so the greater good.
This then is the one species of the Just.
Chapter VII.
And the remaining one is the Corrective, which arises in voluntary as
well as involuntary transactions. Now this just has a different form
from the aforementioned; for that which is concerned in distribution of
common property is always according to the aforementioned proportion: I
mean that, if the division is made out of common property, the shares
will bear the same proportion to one another as the original
contributions did: and the Unjust which is opposite to this Just is
that which violates the proportionate.