Full Idea
A true cause is one in which the mind perceives a necessary connection between the cause and its effect.
Gist of Idea
In a true cause we see a necessary connection
Source
Nicolas Malebranche (The Search After Truth [1675], 1.649 (450)), quoted by Daniel Garber - Leibniz:Body,Substance,Monad 5
Book Reference
Garber,Daniel: 'Leibniz: Body, Substance, Monad' [OUP 2009], p.191
A Reaction
Presumably Hume was ignorant of 'true' causes, since he says he never saw this connection. But then is the perception done by the mind, or by the senses?