The aim of this paper is to provide a logical framework for the specification of autonomous Multi-Agent Systems (MAS). A MAS is autonomous in so far as it is capable of binding ('nomos') itself ('auto') independently of any external normative constraint specified by a designer. In particular, a MAS is autonomous if it is able to maintain its social institutions (i.e. rule-governed social practices) only by way of the agents' attitudes. In order to specify an autonomous MAS, we propose the logic AL (Acceptance Logic) in which the acceptance of a proposition by the agents qua group members (i.e. group acceptance) is introduced. Such propositions are true w.r.t. an institutional context and correspond to facts that are instituted in an attitude-dependent way (i.e. normative and institutional facts). Finally, we contend that the present approach paves the way for a foundation of legal institutions, for studying the interaction between social and legal institutions and, eventually, for understanding and modeling institutional change.
