Full Idea
In "had the acrobat jumped, there would have been a safety net" the antecedent of the counterfactual (the jumping) is temporally later than the consequent (the installation of the net).
Gist of Idea
In some counterfactuals, the counterfactual event happens later than its consequent
Source
Stathis Psillos (Causation and Explanation [2002], §3.3)
Book Reference
Psillos,Stathis: 'Causation and Explanation' [Acumen 2002], p.98
A Reaction
This blocks anyone (e.g. David Lewis) who tries to define counterfactual claims entirely in terms of a condition followed by a consequence. Nice example.