 This leads us to the third doctrine that all individuals in existence undergo motion and flux, namely, substantial motion (haraka jawhariyya). The doctrine follows from his position on existence and his rejection of Aristotle’s category theory. It also demonstrates how he privileges becoming over static, immutable being. Substantial motion is not the same as substances being in motion, which is considered obvious (Rahman 1975: 95–108; Jambet 2006: 191–223; ‘Ubudiyyat 2006: 309–85). Within an Aristotelian framework, there are two types of change: instantaneous such as the move from potentiality to actuality, and gradual such as the ageing process in things that undergo generation and corruption. This raises two objections to substantial motion: first, if existents are constantly motive, how can there be a subject that we recognise as undergoing change? Second, substances are manifest in essences and these cannot be identified in their species form since motion denies the fixity of the species (and genus) boundaries that define the essence. For Mulla Sadra, the second point is easier to treat: essences are not fundamental to which existence is accidental so the boundaries of what we may conceive an essence to be should not limit existence. On the former, existence is its own subject. Drawing upon Aristotelian hylomorphism, he argues that it is the matter of existence that acquires forms as it constantly changes. An existing entity is not a stable substance constant in time to which change occurs as an accident, such as a young Zayd becoming old and greying; rather, it is a structure of unfolding, dynamic events of existence. The young Zayd is thus literally not the same existent as the old Zayd, since the change in him is substantial and existential. One implication of this doctrine is that at every instance each existent is renewed and thus provides a solution to the old problem of time and creation by asserting that the world is created in time, because at each instant all existence is new in time. As such consistent with other Safavid philosophers and in distinction from the earlier Avicennan tradition, he upholds a philosophical account of the theological doctrine of God’s creation of the world from nothing in time. Another implication is to consider time as a dimension of existence, as an analytic property of substantial motion, having no existence independently.