from E.B. 18 pg.475.

In his sketchy account of the process of thinking in De anina ( On the Soul), Aristotle says that the intellect, like everything else, must have two parts: something analogous to matter and something analogous to form. The first of these is the passive intellect; the second is active intellect of which Aristotle speaks tersely. " Intellect in this sense is separable, impassible, unmixed, since it is in its essential nature activity......When intellect is set free from its present conditions it appears as just what it is and nothing more: it alone is immortal and eternal...... and without it nothing thinks."