Aquinas "On the Teacher"

I finally found Aquinas' De Magistro online. I have been wanting to read it for several years but must have been googling wrong. A quote -- it is long, but there is so much in it:

Therefore, just as someone can be healed in two ways -- first by the action of nature only, second by the collaboration of nature and medicine -- so also there are two ways of acquiring knowledge. First, when the mind moves by its own natural power to an understanding of things previously unknown to it. This is called discovery (inventio). Second, when the mind is helped by an outside power of reason. This is called teaching (disciplina).

Now in those things that come about by nature and art, art works in the same way and uses the same sorts of tools as nature. For just as nature uses warmth to heal someone suffering from a cold, so also does a doctor. This is why art is said to imitate nature. Similarly, in the acquisition of knowledge, the teacher leads the student to the knowledge of things the student previously did not know in the same way that someone leads himself to discover what he previously did not know.

The process of discovery begins with applying common self-evident principles to particular subject matters, and then proceeding to some particular conclusions, and then from these moving on to other conclusions. In light of this, one is said to teach another, when he makes clear through certain signs the path (discursum) of reasoning he himself took. Thus the teacher's presentations are like tools that the natural reason of the student uses to come to an understanding of things previously unknown to him.

Therefore, just as the doctor is said to cause health in the sick man with nature working, so also one is said to cause knowledge in another by the activity of the power of reasoning in that person, and this is called teaching. In this way one person is said to teach another and to be his teacher. Thus the Philosopher says that a demonstration is a syllogism causing knowledge.

Now if someone proposes to another certain ideas that are not self-evident or if he does not manifest how they follow from self-evident principles, then he does not cause knowledge in that person, but rather opinion or belief. For those ideas that follow necessarily from the first self evident principles have to be true, and those that are contrary to them have to be false. But to all other ideas he can give his assent or not.