An Informational Theory of Counterfactuals

Backtracking counterfactuals are problem cases for the standard, similarity based, theories of counterfactuals e.g., Lewis (Nous13.4, 455-476, 1979). These theories usually need to employ extra-assumptions to deal with those cases (e.g., Lewis' standard resolution of vagueness). Hiddleston (Nous 39(4), 632-657, 2005) proposes a causal theory of counterfactuals that, supposedly, deals well with backtracking. The main advantage of the causal theory is that it provides a unified account for backtracking and non-backtracking counterfactuals (no extra-assumption is needed). In this paper, I present a backtracking counterfactual that is a problem case for Hiddleston's account. Then I propose an informational theory of counterfactuals, which deals well with this problem case while maintaining the main advantage of Hiddleston's account (the unified account for backtracking and non-backtracking counterfactuals). In addition, the informational theory offers a general theory of backtracking that provides clues for the semantics and epistemology of counterfactuals. I propose that backtracking is reasonable when the (possibly non-actual) state of affairs expressed in the antecedent of a counterfactual transmits less information about an event in the past than the actual state of affairs.