Bartholomew Des Bosses was a Jesuit. Until 1709 he was teaching theology at Hildesheim. Then he spent two years teaching maths at Cologne; then two years teaching theology at Paderborn; and finally he returned to Cologne in 1713.

Des Bosses went to visit Leibniz in Hanover in 1706, and from then on they exchanged long and frequent letters until Leibniz’s death in 1716. After the publication of Leibniz’s Theodicy in 1710, Des Bosses agreed to translate it into Latin, and the translation finally appeared in 1716.

The correspondence was very wide-ranging, and included a lot about China, since Des Bosses was in contact with Jesuit missionaries there. Leibniz was particularly interested in Chinese theological beliefs, and in the I Ching, which he believed proved that the Chinese had discovered binary arithmetic before he had.

From a philosophical point of view, the correspondence is of great importance for revealing Leibniz’s most detailed metaphysical thoughts over the last ten years of his life. He was willing to be quite frank with him, and his emphasis on his phenomenalism is highly significant.

However, there is one major problem. As always, Leibniz was keen to develop a metaphysics which would be acceptable to Protestants and Catholics alike. One of the crunch points was the doctrine of transubstantiation, which didn’t really make sense outside the theories and terminology of scholastic philosophy. This is no doubt one of the reasons for the persistence (even to this day) of scholastic philosophy within the Catholic Church.

What Leibniz did was to propose a sort of optional bolt-on to his metaphysics, which would be consistent with it, but justified only as providing an account of transubstantiation. He called it the ‘substantial vinculum’, or ‘bond’, by virtue of which a compound body could be thought of as something real, and not merely a phenomenon. Since it was something distinct both from monads and from perceptions, the substantial vinculum of the bread could be miraculously changed into the substantial vinculum of Christ’s flesh, without affecting either the underlying monads, or the perceptions of the communicants.

Needless to say, Des Bosses wasn’t convinced. What is remarkable is that a number of Leibniz scholars have been deceived into thinking that Leibniz was expressing what he really believed, and that the substantial vinculum was the cornerstone of his (non-phenomenalist) metaphysics.

I have translated selections from ten of Leibniz’s letters to Des Bosses. They were written in Latin, and I have used Gerhardt’s edition in Philosophischen Schriften, Vol. 2, pp. 291–521.

Go to the Index to the correspondence with Des Bosses