Abstract
This paper attempts to answer whether the property of “efficacy” can be attributed to constitutive rules. In particular, according to Di Lucia, I will point out some problems that the “semantic conception of efficacy” has concerning constitutive and regulative rules. Then, the main goal of the paper will be to reflect on the possibility of the efficacy of constitutive rules by means of a complex case that the semantic conception seems to disregard: The case of the cheater. Does the action of the cheater show the inefficacy of constitutive rules? Does she play the game while breaking the rule? Can the semantic conception of efficacy explain this situation, or do we need a more flexible concept of efficacy that takes nomotropism into account? These are some of the questions I will try to answer.