in certain situations which frequently recur in human life. The rule
prescribes the control and regulation within limits of the agent's
natural impulses to act and feel thus and thus. The situations fall into
groups which constitute the "fields" of the several "moral virtues",
for each there is a rule, conformity to which secures rightness in
the individual acts. Thus the moral ideal appears as a code of
rules, accepted by the agent, but as yet _to him_ without rational
justification and without system or unity. But the rules prescribe no
mechanical uniformity: each within its limits permits variety, and the
exactly right amount adopted to the requirements of the individual
situation (and every actual situation is individual) must be determined
by the intuition of the moment. There is no attempt to reduce the rich
possibilities of right action to a single monotonous type. On the
contrary, there are acknowledged to be many forms of moral virtue, and
there is a long list of them, with their correlative vices enumerated.

The Doctrine of the Mean here takes a form in which it has impressed
subsequent thinkers, but which has less importance than is usually
ascribed to it. In the "Table of the Virtues and Vices," each of the
virtues is flanked by two opposite vices, which are respectively the
excess and defect of that which in due measure constitutes the virtue.
Aristotle tries to show that this is the case in regard to every virtue
named and recognised as such, but his treatment is often forced and the
endeavour is not very successful. Except as a convenient principle
of arrangement of the various forms of praiseworthy or blameworthy
characters, generally acknowledged as such by Greek opinion, this form
of the doctrine is of no great significance.

Books III-V are occupied with a survey of the moral virtues and vices.
These seem to have been undertaken in order to verify in detail the