Whether one man can teach another?

Objections

Objection 1 : It would seem that one man cannot teach another. For the Lord says (Mt. 22:8): "Be not you called Rabbi": on which the gloss of Jerome says, "Lest you give to men the honor due to God." Therefore to be a master is properly an honor due to God. But it belongs to a master to teach. Therefore man cannot teach, and this is proper to God.
Objection 2 : Further, if one man teaches another this is only inasmuch as he acts through his own knowledge, so as to cause knowledge in the other. But a quality through which anyone acts so as to produce his like, is an active quality. Therefore it follows that knowledge is an active quality just as heat is.
Objection 3 : Further, for knowledge we require intellectual light, and the species of the thing understood. But a man cannot cause either of these in another man. Therefore a man cannot by teaching cause knowledge in another man.
Objection 4 : Further, the teacher does nothing in regard to a disciple save to propose to him certain signs, so as to signify something by words or gestures. But it is not possible to teach anyone so as to cause knowledge in him, by putting signs before him. For these are signs either of things that he knows, or of things he does not know. If of things that he knows, he to whom these signs are proposed is already in the possession of knowledge, and does not acquire it from the master. If they are signs of things that he does not know, he can learn nothing therefrom: for instance, if one were to speak Greek to a man who only knows Latin, he would learn nothing thereby. Therefore in no way can a man cause knowledge in another by teaching him.