Full Idea
In the regularity analysis of causes, instead of c causing e, c might turn out to be an effect of e, or an epiphenomenon, or an inefficacious effect of a genuine cause, or a pre-empted cause (by some other cause) of e.
Gist of Idea
Regularity analyses could make c an effect of e, or an epiphenomenon, or inefficacious, or pre-empted
Source
David Lewis (Causation [1973], p.194)
Book Reference
'Causation', ed/tr. Sosa,E. /Tooley,M. [OUP 1993], p.194
A Reaction
These are Lewis's reasons for rejecting the general regularity account, in favour of his own particular counterfactual account. It is unlikely that c would be regularly pre-empted or epiphenomenal. If we build time's direction in, it won't be an effect.