Full Idea
A true cause as I understand it is one such that the mind perceives a necessary connection between it and its effects.
Gist of Idea
A true cause must involve a necessary connection between cause and effect
Source
Nicolas Malebranche (The Union of Body and Soul [1675], p.116)
Book Reference
'The Philosophy of Mind', ed/tr. Beakley,B /Ludlow P [MIT 1992], p.116