Book 6
3
Hence with respect to the qualities of the soul also, it is not enough merely to have established the truth of the above formula; we also have to define exactly what the right principle is, and what is the standard that determines it.Book 6 thus purports to explain further the definition of Moral Virtue (2.615), while at the same time (1.4) continuing the analysis of the definition of Happiness (1.7.15) by examining the Intellectual Virtues.
4
Now we have divided the Virtues of the Soul into two groups, the Virtues of the Character and the Virtues of the Intellect. The former, the Moral Virtues, we have already discussed. Our account of the latter must be prefaced by some remarks about psychology.
5
It has been said before1.13.9. that the soul has two parts, one rational and the other irrational. Let us now similarly divide the rational part, and let it be assumed that there are two rational faculties, one whereby we contemplate those things whose first principles are invariable, and one whereby we contemplate those things which admit of variation: since, on the assumption that knowledge is based on a likeness or affinity of some sort between subject and object, the parts of the soul adapted to the cognition of objects that are of different kinds must themselves differ in kind.
