 Existence is a concept that is innately and immediately grasped in the mind; it requires neither definition (ta‘rif) nor description (rasm) of any sort (Mulla Sadra 2001–5, I: 45–6). Existence is a simple concept that does not have analytically distinct part and hence is not amenable to definition. There was a consensus on this doctrine stemming back at least to Avicenna as it arose out of an Aristotelian conception of essence and the nature of definition. One defines and knows things through their essences but existence has no essence that is singular across its different referents and manifestations. Similarly Mulla Sadra has an extended argument on why existence is not the ultimate genus or class of things (within the context of Porphyry’s five predicables, Mulla Sadra 2001–5, IV: 424ff). Nor is existence a type of a universal to which individual particulars in reality are attached (Mulla Sadra 2001–5, I: 140). He refutes these positions precisely because they were broached by thinkers prior to him who denied any reality corresponding to the concept of existence.