What to read
Citation: Nicolas Malebranche. The Search after Truth. 1712. (Translated and Edited by Thomas M. Lennon and Paul J. Olscamp, Cambridge: Cambridge University Press, 1997).
Read: book 6, part 2, chapter 3 (“The most dangerous error of the philosophy of the ancients”), paragraphs 8-17, pp. 448-50.
What to look for
Malebranche denied that natural bodies can bring about effects. Instead, a natural cause, such as one billiard ball’s touching the other, is only the occasion for God’s bringing about the effect. God’s omnipotence (infinite power) is the only explanation of how changes come about.
This reading contains a series of arguments purporting to show that this is so. They focus on the inability of finite minds, such as ours, to bring about effects in the physical world but the point was about any natural object, whether physical or mental.
Hume agreed with Malebranche that we do not understand how natural bodies cause effects. But, note, by the same token, we do not understand how God causes effects either.