  But if we attribute the doctrine of superessentialism to Leibniz, then it would seem that there will be a difficulty in distinguishing those properties that traditionally were thought to be essential to an individual and those that were thought to be mere accidents. In other words, if all properties are essential, on Leibniz's view, is there any difference between his humanity and his wearing a fluffy silk shirt on 1 January 1700? Not surprisingly, Leibniz has a solution to this apparent problem. In an important work on logic from the period of the Discourse on Metaphysics and Correspondence with Arnauld, the General Inquiries about the Analysis of Concepts and of Truths (Generales Inquisitiones de Analysi Notionum et Veritatum, 1686), Leibniz makes the standard, Aristotelian distinction between essential properties and accidents, saying “that thing which is called ‘a man’ cannot cease to be a man except by annihilation; but someone can begin or cease to be a king, or learned, though he himself remains the same.” (A VI iv 740/LLP 47) The important point here is the species to which an individual belongs contributes one level of properties to an individual; but, of course, these are properties that are held in common by all members of that particular species. Therefore, for example, Adam is not only a man, but necessarily also rational and, to use the Aristotelian chestnut, a featherless biped. Following Mondadori (1993), let us call being a human being a specific essential property. But there may also be individuating essential properties, those which single x out from the other members of the same species and which are nevertheless such that, lacking them, x would no longer be x. For example, consider several counterpart Adams: one who brought no sin into the world, one who did so by eating the forbidden donut, etc. As we have said, they cannot be identical to Adam@, which is another way of saying that Adam@ would cease to be Adam@ if he no longer brought sin into the world by eating the forbidden fruit. But now consider a Plantinga-inspired example: the alligator who brought sin into the world. Could the alligator count as a counterpart of Adam@? No, for lacking the property of humanity, there are simply no counterparts of Adam@. In support of this view, consider On Freedom, Fate and the Grace of God (De libertate, fato, gratia Dei, 1686/87), where Leibniz first has a critic of his view say that, “God … has in his intellect a notion or an idea of Peter as perfect as possible containing all truths concerning Peter, the objective reality of which constitutes the complete nature or essence of Peter, and accordingly, to deny is essential to Peter and is foreknown by God.” Leibniz's response employs the distinction between necessary and contingent properties: