 Sensibility, then, would seem to be proof of the soul’s radical inability to remain in itself, as opposed to the intellect, which is immobile and in actuality by its own nature (another sign of the fact that the unity of the soul is no longer considered self-evident is the introduction of the so-called “vehicle” of the soul, a spiritual garment that acts as an interface between the soul and bodies: on this subject, cf. Finamore 1985). What stands out as most remarkable is the notion that the soul’s essence is also challenged in the course of sensitive acts. Iamblichus here inherits the Aristotelian terminology of Essence/Substance (ousia)—Power (dynamis)—Activity (energeia): a single essence—say, the human soul—acts as a substratum for a plurality of powers (sensitive, intellective, imaginative, etc.), and those powers are in turn actualized in a greater plurality of activities (sense-perception, aisthēsis, of x, y, or z; intellection, noēsis, about x, y, or z). These three terms are hierarchised, insofar as the soul can remain inactive: but in Aristotle, this hierarchy remains largely implicit, contrary to Iamblichus and his unequivocal conception of vertical causality (see above,  Section 3.5).  In applying his own principles, Iamblichus argues that, since the effect is nothing outside of its cause, any flaw connatural to the effect would also have to be preassumed in the cause. Since, then, the soul’s activities show instability and imperfection, this inability to act consistently and permanently points to a break in its very essence (cf. De anima sect. C [DF-2002] = pseudo-Simplicius, In De anima 89.33–35).