The logicians, however, claim that a complete definition is intended to make the essence known, and that the essence consists of the essential attributes included within the thing defined—namely, genus and differentia. They divide the attributes inseparable from a subject into those that form part of its essence and those that lie outside it and are accidental. They further divide these inseparable accidental attributes into two kinds: those inseparable from the quiddity and those inseparable from the existence of the quiddity. They base this approach on the claim that the quiddities of things—which are their essences—subsist in external reality and are distinct from the particular entities existing there. They also claim that essential attributes precede the subject both in the mind and in external reality, and constitute parts that precede the subject’s essence in both modes of existence: mental and external.

This and similar views are mistaken according to the vast majority of rational thinkers, among Muslim speculative thinkers and others. Rather, Muslim speculative thinkers hold that attributes fall into two categories: those inseparable from the subject, which cannot be absent unless the subject itself ceases to exist; and those that are incidental to it and can cease to belong to it while the subject itself continues to exist. These inseparable attributes include those inseparable from the individual, but not from its species