Full Idea
Important relations are duration (order of successive things) and position (order of coexisting things) and interaction. Position without a thing mediating is presence. Beyond these is connection when things move one another. Thus things seem to be one.
Gist of Idea
Things seem to be unified if we see duration, position, interaction and connection
Source
Gottfried Leibniz (Letters to Des Bosses [1715], 1712.02.05)
Book Reference
Leibniz,Gottfried: 'Philosophical Essays', ed/tr. Arlew,R /Garber,D [Hackett 1989], p.199
A Reaction
[compressed] This is the best account I can find of his epistemological angle on the unity of things. They are symptoms of the inner power of unification, and he says that God sees these relations most clearly.