As to the order in which the different departments should he studied,
we have had preserved to us the actual words of Chrysippus in his
fourth book on Lives. 'First of all then it seems to me that, as has
been rightly said by the ancients, there are three heads under which
the speculations of the philosopher fall, logic, ethic, physic; next,
that of these the logical should come first, the ethical second, and
the physical third, and that of the physical the treatment of the
gods should come last, whence also they have given the name of
"completions" to the instruction delivered on this subject'. That
this order however might yield to convenience is plain from another
book on the use of reason, where he says that 'the student who takes
up logic first need not entirely abstain from the other branches of
philosophy, but should study them also as occasion offers.'

Plutarch twits Chrysippus with inconsistency, because in the face of
this declaration as to the order of treatment, he nevertheless says
that morals rest upon physics. But to this charge it may fairly be
replied that the order of exposition need not coincide with the order
of existence. Metaphysically speaking, morals may depend upon physics
and the right conduct of man be deducible from the structure of the
universe but for all that, it may be advisable to study physics
later. Physics meant the nature of God and the Universe. Our nature
may be deducible from that but it is better known to ourselves to
start with, so that it may be well to begin from the end of the stick
that we have in our hands. But that Chrysippus did teach the logical
dependence of morals on physics is plain from his own words. In his
third book on the Gods he says 'for it is not possible to find any
other origin of justice or mode of its generation save that from Zeus
and the nature of the universe for anything we have to say about good