 One of the single most important theoretical revisions of the Aristotelian model concerns the notion of necessity (ḍarūra), which in fact takes on a new role in Avicenna’s system in a number of different ways. At a general level, there is an epistemic notion associated with the idea of certainty mentioned above; then there is a technical sense involved in Avicenna’s reading of necessity statements (which are unsurprisingly a major ingredient of scientific theories); and finally there is a notion of necessity associated with scientific predication, which in a way is the most fundamental of all.