One of the most curious features of Leibniz's late metaphysics is no doubt the idea of the substantial bond, or vinculum substntiale. Apparently out of the blue, in his correspondence with the Jesuit philosopher, Bartholomew des Bosses, Leibniz posits some kind of thing that will explain transubstantiation, "realize" or "reify" phenomena and ground the reality of corporeal or composite substances.
Despite its oddity, the vinculum substantiale has received relatively little critical attention, and when the vinculum is mentioned in expositions of the Leibniz's thought, it is usually brushed over or unceremoniously dismissed as Leibniz's disingenuous attempt to explain transubstantiation to his Catholic friend, Des Bosses.1 Indeed, Bertrand Russell, who set the tone for English-language commentators on Leibniz, says that Leibniz's theory of the vinculum substantiale [End Page 203] is "more the concession of a diplomatist than the creed of a philosopher."2 And the subtext of Russell's criticism is simply that, because the idea of the vinculum substantiale arises in a discussion of transubstantiation (and only with the Jesuit Des Bosses), we ought not to take the idea seriously. This view, the "Russell-Dismissal," as I shall call it, has become something of the standard view on the subject, to the extent that one may speak of a standard view at all.
In this paper, I shall not directly address the question, Did Leibniz believe in the vinculum substantiale? I think that the safest answer to this question is that Leibniz experimented with the idea of the vinculum substantiale in order to solve problems in his monadology relating to the nature of composite substance but did not ultimately regard the vinculum substantiale as a real feature of his metaphysical system.3 The question I do want to address is even more fundamental—namely, what is the vinculum substantiale anyway? What did Leibniz understand the vinculum substantiale to be? This question is far more difficult to answer, and, in my opinion, it has not only never been answered satisfactorily, it has never been approached rigorously.4
I think that if we come to a better understanding of what Leibniz meant by the vinculum substantiale, then we will not only be able to appreciate the problems that prompted Leibniz to consider the vinculum but we will also be able to approach the question of his commitment to the vinculum in a much more interesting and helpful way. To give away a part of the answer in advance: we shall see that the idea of the vinculum is such that Leibniz certainly should not have held it. A further interesting factor in my interpretation of the vinculum substantiale is the way in which it corrects the "Russell-Dismissal." As I shall argue, if one dismisses the discussion of transubstantiation, one misses some of the crucial features of the vinculum substantiale, and one further misses the fact that Leibniz argues strongly against the view suggested by Des Bosses.
Before turning to a detailed discussion of the nature of the vinculum substantiale, I shall in the following two sections explain the role of the vinculum in Leibniz's account of transubstantiation and in his account of the nature of composite substance. In the heart of the paper, §4, I shall present four models [End Page 204] for the vinculum substantiale: the vinculum substantiale as substantial form, as relation, as composite substance, and as separate, substance-like thing. Each model can be seen to follow from some passage in the Leibniz-Des Bosses correspondence, but I shall try to argue that the model that is consistent with the majority of texts and that makes the most sense of Leibniz's discussion of transubstantiation and the nature of composite substance is that of the vinculum substantiale as separate or independent substance-like thing.
2. The Vinculum Substantiale and Transubstantiation
It is no accident that the vinculum substantiale is associated with Leibniz's account of transubstantiation in his correspondence with Des Bosses. Des Bosses sought to understand how Leibniz, in his world of monads, could explain transubstantiation or the real presence of Christ in the Eucharist, and in his...