Chapter 117 - Of What Belongs to Human Actions
To teach is to be the cause of knowledge in the learner, by bringing him from potentiality into act ministerially, in the first place by giving him the light of the less universal propositions which are easily known by first principles, or sensible signs, or the like examples or their opposites, whereby he is led on to knowledge; secondly, by strengthening the intellect, not by any active power, but by giving the right method of principles to their conclusions; whereas probably of himself he could not exercise the power of comparison sufficiently to reach the conclusions. Hence it follows that the teacher's office is external, as in the same way a doctor cures disease by medicines.
Likewise men do not teach the angels, but only speak to them; for men are to angels, as the inferior angels are to the superior; and the inferior do not enlighten the superior, but manifest their thoughts by a sort of locution; and men act in the same way.
The soul cannot by its natural power make any change in corporeal matters; because it is only from God the First Cause, virtually containing the matter and form, and by an agent compounded of matter and form, that such a change can be made. The angels produce such change only by the application of some corporeal agent: much less can the soul do so, when we speak of direct change; but indirectly it can work a change in the body belonging to it, as appears in the apprehension of the soul as regards the sensitive appetite, in fear, and the like; and also we see how the sensible life of the body is affected by the imagination, especially the eyes, where sense is prominent. Neither is a body subject to the separated soul by the force of the latter; for as the soul is determined to vivify the body and move it, a dead member has no longer subjection as regards local motion. Apart from and above this natural power it may receive power from a Divine Source. The demons often pretend to be souls, for the purpose of deluding and deceiving men, as happened to Simon Magus.