We are a Working Group devoted to the discussion of historical and philosophical issues in symbolic logic, mathematics, and science. We meet on occasional Wednesday evenings for a talk and a lively discussion. The group is funded by the Doreen B. Townsend Center for the Humanities and the Department of Philosophy.

All members of the academic community are welcome to attend. We have regular participants in many different fields, including philosophy, mathematics, history of science, and psychology.

The group organizers are Lara Buchak (Philosophy), Wesley Holliday (Philosophy), John MacFarlane (Philosophy), Paolo Mancosu (Philosophy), and Seth Yalcin (Philosophy).

Our next event

March 14, 2018, 6-7:30 PM in 234 Moses Hall

Alan Hajek (Australian National University)

Most Counterfactuals Are Still False

I have long argued for a kind of ‘counterfactual scepticism’: most counterfactuals are false. I maintain that the indeterminism and indeterminacy associated with most counterfactuals entail their falsehood. For example, I claim that these counterfactuals are both false:

  • (Indeterminism) If the chancy coin were tossed, it would land heads.

  • (Indeterminacy) If I had a son, he would have an even number of hairs on his head at his birth.

And I argue that most counterfactuals are relevantly similar to one or both of these, as far as their truth-values go. I also have arguments from the incompatibility of ‘would’ and ‘might not’ counterfactuals, and from so-called ‘reverse-Sobel sequences’.

However, counterfactual reasoning seems to play an important role in science, and ordinary speakers judge many counterfactuals that they utter to be true. A number of philosophers have defended such judgments against counterfactual scepticism. David Lewis and others appeal to ‘quasi-miracles’; Robbie Williams to ‘typicality’; John Hawthorne and H. Orri Stefánsson to ‘counterfacts’, primitive counterfactual facts; Moritz Schulz to an arbitrary-selection semantics; Jonathan Bennett and Hannes Leitgeb to high conditional probabilities; Karen Lewis to contextually-sensitive ‘relevance’.

I argue against each of these proposals. A recurring theme is that they fail to respect certain valid inference patterns. I conclude: most counterfactuals are still false.