Full Idea
It isn't sufficient to say that God has made a general law, for in addition to the decree there has also to be a natural way of carrying it out. It is necessary, that is, that what happens should be explicable in terms of the God-given nature of things.
Gist of Idea
In addition to laws, God must also create appropriate natures for things
Source
Gottfried Leibniz (Letter to the Editor about Bayle [1698], p.205)
Book Reference
Leibniz,Gottfried: 'Philosophical Texts', ed/tr. Woolhouse R/Francks,R [OUP 1998], p.205
A Reaction
Thus Leibniz is an ancestor of scientific essentialism, but he was too frightened to take the next step, which is to see that once God has endowed the natures, he doesn't need to wield his laws as well. The natures will do the whole job.