Deterministic Models and the “Unimportance of the Inevitable”

Abstract

In some appreciated essays of the 1980s Jon Elster threw light on the conceptual difficulty which he described as "the basic paradox of counterfactuals": the stronger (more deterministic) is the connection between antecedent and consequent of a counterfactual, the weaker is the legitimacy of the antecedent. The aim of the present paper is to show that Elster's thesis rests on several confusions, the most important of which is the one between a theory and a model. When a model is deterministic, only several theoretical extra assumptions allow to qualify a counterfactual supposition as an illegitimate one. In particular, it is argued that only special auxiliary assumptions may allow or forbid drawing nontrivial conclusions from suppositions which are "counterpossible"--i.e., such as to deny something which the theory asserts to be necessary--or "counterlegal", i.e., implying the falsity of a law belonging to the model itself.