Aquinas on Aristotle

Aquinas studied Aristotle like no other man had before or since and he used Aristotle to justify his entire thinking.

Aquinas' theory of knowledge is not a vision of divine truth -- you might expect that coming from this very Christian saint.
Rather, his theory of knowledge is a sober statement of how men know the world.

Man is a rational animal and the world can be understood by human reason. 

A being endowed with reason, man can understand the universe. 

But as an animal, man can know only that which he can experience with his senses.

This is Aristotelianism to the core.

As Aquinas himself put it: "whatever is known is known in the manner in which man can know it."

This is a fundamental principle of all knowledge according to Aquinas and could lead man in two directions:

1. man can know of the world only that which he learns from his experience of the material world. This brand of empiricism sets limits to what we can know. For Aquinas, this raised the question: "how can we reconcile faith and reason?"
2. the world is intelligible to rational man. Whatever exists, can be understood. Whatever exists, has a set of causes. These causes are known only through man's experience and his reflection upon that experience.

To find these principles or first causes is the whole object of our knowledge. 

What experience conveys can be put into language and expressed in words, propositions and demonstrations.

Though man cannot say all that the world is, what he can say is truly said.

This is a theory of the function of the individual knower. 

The mind knows itself, knows its objects, and finally, the mind knows its own nature.

[from 'Aquinas and Dante', ;http://www.historyguide.org/ancient/lecture28b.html