 The hallmark of natural philosophy and indeed of any science (sing. Gk. epistēmē, Ar. ʿilm) for Avicenna and the entire Aristotelian tradition is to uncover and to grasp the basic causes (sing. ʿilla) of the phenomenon under consideration. Like Aristotle before him, Avicenna identifies four sorts of causes: the matter, form, agent (or efficient cause) and end (or final cause) (Avicenna, [Ph], 1.10 and Avicenna, [MPh], bk. 6). For Avicenna the material cause is a wholly inert substratum for form. The matter explains any passivity or potentiality to be acted upon that a body might have. The form (ṣūra) is the cause, primarily, of a body’s being the actual kind or species that it is and performing the various actions associated with that species; secondarily, a form might be the cause of the accidental features and determinations that belong to that body (Avicenna occasionally uses hayʾa for this second sense of form). In general then, the form is the cause of any actuality, that is positive features or actions, that the body has or does. The efficient cause accounts for a body’s undergoing motion and change (or even for its existence), while the final cause is that for the sake of which the form occurs in the matter. 