for here too the first task is that of determining the concept of the subject in the traditional sense as a truncated subject, though indeed in an essentially deeper and extended sense. As a consequence of this monadological interpretation of the subject, Leibniz arrives at a particular view concerning the possible commerce between subjects, the exchange between them. The being with one another of human and human is an instance of the exchange between substances in general.
We can consider Leibniz’s Monadology only briefly, so as to contrast it with the above interpretation of Dasein and being with one another and thereby to provide a summary clarification of what was said there, by way of comparison. Certainly, it could also be shown how the Monadology first displays the richness and depth of its conception precisely if one does not simply attempt to grasp it starting from the traditional concept of the subject, a concept that Leibniz himself so little overcomes through the Monadology that he rather precisely presupposes it for this. Aside from that, however, the Leibnizian monad is one of the boldest ideas ever to emerge in philosophy since Plato.
Leibniz designates substances as monads—in Greek, monas = unity—as unities. Unity means: simplicity, that which is originary, determinative of the whole, individuality; τόδε τι, Aristotle’s οὐσία. ἕν—ὄν—οὐσία, cf. Metaphysics Γ 2, 1003 b23/b32. In the ancient doctrine of Plato and Aristotle, every being, as a being, is in each case one; it is constituted by a quite specific unity. According to Leibniz, the being of each and every being is properly grounded in this specific unity. For Leibniz, monas is that which originarily gives unity, the simple that unifies and, as unifying, individuates. For this reason, he designates every independent being with regard to this primary determination of unity a monad: the unity that unifies simply and in advance and thereby individuates.
The problem of the monad is thus nothing other than the revisited problem of the substantiality of substance or, as we can also say, of the subjectivity of the subject; for in Leibniz, as fundamentally also still in Kant, subject means subiectum, that which underlies, ὑποκείμενον, that which is of its own accord. According to Leibniz, all monads, all substances—including corporeal substances—thus, the elementary particles of a body, have a soul.
That the monad has a soul means: monas has vis, urge, nisus; appetitus, repraesentatio. It is unifying from the ground up, taking into unity in advance and maintaining what it represents; every monad in each case mirrors the totality of beings, though each from a different point of view and differing in degrees of awakeness. There are dull, drowsy, slumbering monads that constitute the corporeal as such. From these, there is a scale leading up to God, the central monad, God conceived according to Christian theology. From here, one can understand why Leibniz designates every monad as a speculum vitale, a living mirror.
In urge itself, in what and how the monad itself is, it in each case procures for itself this view of the whole, seen from a particular point of view. Insofar as each monad of its own accord represents the whole from a particular point of view, it