of the natures of these differentiae, just as it is a necessary concomitant of these species, then, when the concomitant and that which entails it are considered in their concrete external existence, the entailment is mutual: the existence of either entails the existence of the other, and its absence entails the other’s absence. Neither, therefore, can be said to be more general or more specific than the other.

If it is said that they share animality, while each is distinguished from the other by rationality and the capacity to neigh, respectively, then each of these existing beings is distinguished from others by its animality, just as it is distinguished by its rationality or its capacity to neigh. Rationality at the level of species does not distinguish one particular individual from another; it distinguishes only one species from another. Species exist only in minds, not in concrete external things. For if being an animal necessarily accompanies being rational or capable of neighing, the animal itself is the very being that neighs and the very being that is rational; the animal is not something within it.

They may say that there is an animal within the rational being and the neighing being. This is mistaken, for the animal is itself what is described as neighing or rational. Within a particular substance there is no other substance, whether unqualified or particular. Rather, it is a single substance characterized by both these attributes. Moreover, this particular neighing being is an animal, but it is not that particular neighing being which is an animal, let alone that particular rational being.