 On the other hand, it appears that a universal is also a composite. Every universal except for the most general of genera, can be said to be “composed” out of a genus and a differentia. These parts are sometimes called “essential” parts of the universal since the genus and differentia together constitute the essence of the universal (Aquinas Summa Theologiae I, q. 8, art. 2, ad 3; and I q. 76, art. 8), although to avoid confusion we perhaps ought to call them definitional parts. The essence of a universal is usually encoded in its definition. For example, the definition of Human Being is rational mortal animal. Animal is the genus, and rationality and mortality are the differentiae. 