Virtue is to be understood from the constitution of human nature.

In man, there is a lower and a higher faculty of Desire; or, otherwise expressed, there are the various affections that have their roots in sense and centre in self-love or the desire of self-preservation, and there is also a natural love of justice implanted from the beginning.

In proportion as the _appetitus justi_, which consists in will, gains upon the _appetitus commodi_, men become more worthy of a larger happiness.

Self-love rules in man, so long as he is in the natural state of sin; if, amid great conflict and by divine help, the higher affection gains the upper hand, the state of true virtue, which is identical with the theoretic state of belief, and also of pure love to God and man, is reached.
By the middle of the thirteenth century, the schoolmen had before them the whole works of Aristotle, obtained from Arabian and other sources.
Whereas, previous to this time, they had comprehended nearly all the subjects of Philosophy under the one name of Dialectics or Logic, always reserving, however, Ethics to Theology, they were now made aware of the ancient division of the sciences, and of what had been accomplished in each.

The effect, both in respect of form and of subject-matter, was soon apparent in such compilations or more independent works as they were able to produce after their commentaries on the Aristotelian text.