The school of Theodorus, as I
have said, groups everything under heads,
they mean several things. First they mean the main
which is to be identified with the basis;
secondly they mean the other questions dependent
on the main question,
thirdly the proposition
statement of the proofs.
The word is used as we use it
when we say “It is the head of the whole business,”
or, as Menander says, κεφάλαιόν ἐστιν.1
speaking, anything which has to be proved will be a
head of varying degrees of importance.
I have now set forth the principles laid down by
the writers of text-books,