Full Idea
Counterfactuals are important for reasoning about the past and to plan for the future. If we want to learn from our mistakes, it is important to think about what would have happened if I had done things differently.
Gist of Idea
Counterfactuals are essential for planning, and learning from mistakes
Source
Thomas Hofweber (Ontology and the Ambitions of Metaphysics [2016], 13.4.1)
Book Reference
Hofweber,Thomas: 'Ontology and the Ambitions of Metaphysics' [OUP 2018], p.326
A Reaction
A thought also found in Tim Williamson, but not the sort of thing you hear from Lewis or Stalnaker. It is a nice example of how highly abstract and theoretical problems need to be slotted into human psychology.