a scribe and that one a jurist, yet such a trait cannot be deemed an inseparable attribute, for one and the same nature does not entail mutually divergent properties. If the point on which they differ is merely contingent to that nature, its cause must be something other than the shared essence in which they agree. Upon close scrutiny, discourse of this sort boils down to sheer sophistry and obfuscation.
Suppose, then, you treat it as a genus like “animal” and say that its species—man and horse—share a necessary attribute such as animality, or an accidental one such as nourishment and motion. The confusion here is that the proponent has not distinguished between an accident inseparable from the essence or from its concrete existence and an accident that may detach from it. It is well known that, according to their celebrated Greek logical terminology, they draw a line between the essential and the accidental—whether the accident is inseparable from the essence or only from existence. We have already exposed elsewhere the invalidity of this distinction; we have debated it with more than one of their leading figures, granted them ample time to review the writings of their own masters and to consult one another, yet it became clear that the distinction they advance has no reality beyond an arbitrary convention with no grounding in objective fact and no knowledge truly corresponding to its object.
Nevertheless, for the moment we shall address them on the basis of their own terminology. You maintain, for example, that rationality is an essential inseparable of man, whereas laughter is an accidental inseparable; and on that basis you differentiate between the essential definition, in which the specific differentia is cited along with the genus, and the descriptive definition, in which the specific property replaces the differentia—whether mentioned with the genus or with a common accident. You regard discussion of these five universals—genus, species, differentia, specific property, and common accident—as foundational to your science, calling it the “mother.” And you say that blackness in tar or the raven, or the shadow of a horse at sunrise, and similar cases, is inseparable from existence rather than from essence; yet both of them