The Weekly Newsletter of MIT Linguistics

LFRG 4/7 - Justin Khoo

Speaker: Justin Khoo (MIT Philosophy)
Title: Backtracking counterfactuals, revisited
Date/Time: Monday, Apr 7, 12-1:30p
Location: 66-148

Backtracking interpretations of counterfactuals are weird, but very real. Under a backtracking interpretation, we evaluate the counterfactual by making the requisite changes to how its antecedent would have had to have come about, and then play out the resulting scenario to see whether its consequent would thereby be made true.

For instance, consider the following scenario from Frank Jackson: you see your friend Smith on the ledge of the roof of a twenty story building, poised to jump. Thankfully, he doesn’t! You feel relief, and say to yourself,

(1) If Smith had jumped, he would have died.

It seems pretty clear that the counterfactual you utter is true. Yet now suppose that a mutual friend Beth is also on the scene. Beth objects to your claim on the following grounds. “Smith would have jumped only if there had been a net below to catch him safely. Hence, (1) is false, and instead the following is true:

(2) If Smith had jumped, he would have lived.”

Beth’s utterance of (2) is true on its backtracking interpretation, while your utterance of (1) is true on its non-backtracking interpretation.

I am interested in the conditions under which backtracking interpretations of counterfactuals arise and why they only arise in such conditions. Related to this is the following troubling issue: given that counterfactuals are so semantically flexible, how do we ever communicate using them?