Asserting the reality of a human nature, one and the same in all men, does not imply belief in any Platonic type. It is in the mind alone that human nature, or any nature, possesses a condition of positive unity. In the real the features which make up the universal human nature exist in the state of individuality, which means that human nature exists in James as identical with the individual reality of James. The same human nature exists in Philip in the state of individuality, which means that it exists in Philip as identified with the individual reality of Philip. (Yet James is not identical with Philip. As John of St. Thomas says, two things each of which is identical with the same third thing are not necessarily identical with each other if the third thing is virtually multiple: "But the universal nature is virtually multiple because it is communicable to several things; therefore, identity with it does not entail the identity of the individuals among themselves.") Inasmuch as it is the same human nature, made of the same intelligible features connected with one another in the same system of intelligibility, which exists in the real as identified with James and as identified with Philip, James and Philip are one in nature and are equal in an essential and fundamental sense, regardless of the inequality of their individual properties. From the very instant of their creation men are different and unequal in countless respects; yet it is highly proper that they should be described as created equal, for in each of them the same system of intelligible features supplies the individual with ability to exist.
Yves R. Simon, The Philosophy of Democratic Government, IV.1.
