Full Idea
The 'influx' model of causation says that causes involve a process of contagion, as it were; when the kettle boils, the gas infects the water inside the kettle with its own 'individual accident' of heat, which literally flows from one to the other.
Gist of Idea
The old 'influx' view of causation says it is a flow of accidental properties from A to B
Source
report of Francisco Suárez (works [1588]) by Nicholas Jolley - Leibniz Ch.2
Book Reference
Jolley,Nicholas: 'Leibniz' [Routledge 2005], p.56
A Reaction
This nicely captures the scholastic target of Hume's sceptical thinking on the subject. However, see Idea 2542, where the idea of influx has had a revival. It is hard to see how the water could change if it didn't 'catch' something from the gas.
Related Idea
Idea 2542 Causation in the material world is energy-transfer, of motion, electricity or gravity [McGinn]