The human intellect is in potency and moves to act. All that which passes from potency to act necessitates an agent of the same species as the thing that must pass on to the act. The intellect as well, therefore, in order to pass from potency to act, needs an active intellect which is always in act and never in potency. When man’s intellect reaches its extreme perfection, it comes close in its substance to the substance of this active intellect. In its search for perfection, man’s intellect tends to imitate the model of this intellect, since it is that which makes man substantial in so far as he is man. This intellect is also man’s end because it is that which provides him with a principle and an example to follow in tending to perfection, which consists in approximating himself as far as it is possible to it. It is therefore his agent, his end, and his perfection. It is a principle in three different ways: as an agent, as an end, and as the perfection to which man tends. It is, however, a separate form with respect to man, a separate agent, and a separate end.