city, still more will it not compel any one to turn off the water
in the city." Again, on the other hand: "Whatever is valid in a
smaller matter ought to be valid also in a greater one. One may
convert the preceding example." Also, "That which is valid in a
parallel case ought to be valid in this which is a parallel case." As,
"Since the usurpation of a farm depends on a term of two years, the
law with respect to houses ought to be the same." But in the law
houses are not mentioned, and so they are supposed to come under the
same class as all other things, the property in which is determined by
one year's use. Equity then must prevail, which requires similar laws
in similar cases.[64]

But those arguments which are derived from external circumstances
are deduced chiefly from authority. Therefore the Greeks call
argumentations of that kind [Greek: atechuoi], that is, devoid of
art. As if you were to answer in this way:--"In the case of some one
building a roof for the purpose of covering a common wall, Publius
Scaevola asserted that there was no right of carrying that roof so
far that the water which ran off it should run on to any part of any
building which did not belong to the owner of the roof. This I affirm
to be law."

V. By these topics then which have been explained, a means of
discovering and proving every sort of argument is supplied, as if they
were elements of argument. Have we then said enough up to this point?
I think we have, as far at least as you, an acute man and one deeply
skilled in law, are concerned. But since I have to deal with a man who
is very greedy when the feast in question is one of learning, I will
prosecute the subject so that I will rather put forth something more
than is necessary, than allow you to depart unsatisfied. As, then,
each separate one of those topics which I have mentioned has its own
proper members, I will follow them out as accurately as I can; and
first of all I will speak of the definition itself.

Definition is a speech which explains that which is defined. But of
definitions there are two principal kinds: one, of those things which
exist; the other, of those which are understood. The things which I
call existing are those which can be seen or touched; as a farm, a
house, a wall, a gutter, a slave, an ox, furniture, provisions, and so
on; of which kind of things some require at times to be defined by us.
Those things, again, I say have no existence, which are incapabl