Full Idea
To show the semantic difference between counterfactuals and indicative conditionals, 'If Booth hadn't shot Lincoln someone else would have' is false, but 'If Booth didn't shoot Lincoln then someone else did' is true.
Gist of Idea
'If B hadn't shot L someone else would have' if false; 'If B didn't shoot L, someone else did' is true
Source
Theodore Sider (Logic for Philosophy [2010], 8)
Book Reference
Sider,Theodore: 'Logic for Philosophy' [OUP 2010], p.199
A Reaction
He notes that indicative conditionals also differ in semantics from material and strict conditionals. The first example allows a world where Lincoln was not shot, but the second assumes our own world, where he was. Contextual domains?