Full Idea
Given our present knowledge of the laws of nature, we can imagine ways of controlling floods by controlling rainfall, but not the other way round. That is should be so, however, is contingent.
Gist of Idea
We can imagine controlling floods by controlling rain, but not vice versa
Source
G.H. von Wright (Logic and Epistemology of Causal Relations [1973], §8)
Book Reference
'Causation', ed/tr. Sosa,E. /Tooley,M. [OUP 1993], p.119
A Reaction
Despite my objections to Idea 8363, this is a good example. It won't establish the metaphysics of the direction of causation, though, because God might control rainfall by controlling floods. Maybe causation is more like a motorway pile-up than dominoes.
Related Idea
Idea 8363 p is a cause and q an effect (not vice versa) if manipulations of p change q [Wright,GHv]