Full Idea
The correct definition of the causal relation is to be framed in terms of one single case of sequence, and constancy of conjunction is therefore no part of it.
Gist of Idea
Causation is defined in terms of a single sequence, and constant conjunction is no part of it
Source
Curt Ducasse (Nature and Observability of Causal Relations [1926], Intro)
Book Reference
'Causation', ed/tr. Sosa,E. /Tooley,M. [OUP 1993], p.125
A Reaction
This is the thesis of Ducasse's paper. I immediately warm to it. I take constant conjunction to be a consequence and symptom of causation, not its nature. There is a classic ontology/epistemology confusion to be avoided here.