B. Solution of the Question by Maintaining the Third Way

69. By maintaining the third way (which seems to attribute more to the habit), it can thus be said that, just as, if there were some heaviness in a stone that would not be a sufficient active principle with respect to descent downwards, yet it would be a partial active principle (as will be said in II d.2 p.2 q.6 nn.2-11 about a sufficient heaviness, because it is a total active principle with respect to descent downwards), that - I say -diminished heaviness, along with another moving power moving it to the descent, could act in a diminished way, such that, with the other moving power acting with equal effort, the descent that is caused by that other extrinsic moving power and by the diminished heaviness moving intrinsically would be quicker than a descent that is caused by the extrinsic moving power alone moving with equal effort, yet the extrinsic moving power could, with so much effort, move a neutral body (namely one which had no heaviness or lightness), just as this body would be moved by intrinsic heaviness and by an extrinsic moving power acting weakly; - so, in the proposed case, the habit moves the power as a sort of weight, which, however, is of itself not sufficient for actively eliciting the operation, but the virtue alone of the active power, without such weight, is sufficient; but when both come together, yet such that there is not on the part of the power a greater effort now than before, a more perfect operation is elicited now than could be elicited before by the power itself alone.

70. And common experience seems to be in favor of this way, because anyone can experience that, when he has been habituated, he can with equal effort have a more perfect operation than he could have when not habituated (which perfection of the act could not be attributed to the habit, if the habit were only an inclining passive principle), because at any rate, as it seems, in the prior instant of nature in which the operation is elicited - before it is received in the power - there would be an equal idea of active principle in the eliciting, and so a perfect operation would be elicited with equal effort by an habituated and by a non-habituated power.