Here’s another way of putting it. Imagine that you are deciding whether to support a project P with some action A. Lots of other agents have been involved in P and have contributed more than you in the past. You can make some small contribution (action A) which tips the balance making P a success, producing $1bn benefits, otherwise P fails. Should I say “by acting I personally will ensure that $1bn are produced”? Or should I say that “by acting I personally will ensure that $1bn divided by other’s contributions are produced?” The difference between my acting and not acting is $1bn, so the former.
Simply, the term ‘counterfactual impact’ refers to the difference between the world in which I act and the world in which I don’t.
Here’s another way of putting it. Imagine that you are deciding whether to support a project P with some action A. Lots of other agents have been involved in P and have contributed more than you in the past. You can make some small contribution (action A) which tips the balance making P a success, producing $1bn benefits, otherwise P fails. Should I say “by acting I personally will ensure that $1bn are produced”? Or should I say that “by acting I personally will ensure that $1bn divided by other’s contributions are produced?” The difference between my acting and not acting is $1bn, so the former.
Simply, the term ‘counterfactual impact’ refers to the difference between the world in which I act and the world in which I don’t.