This paper examines a fundamental philosophical difference between two radical postcognitivist theories that are usually assumed to offer (more or less) the same view of cognition; namely the autopoietic theory (AT) and the enactive approach. The ways these two theories understand cognition, it is argued, are not compatible nor incompatible but rather incommensurable. The reason, so it is argued, is that while enactivism, following the traditional stance held by most of the cognitive theories, understands cognitive systems as constituting a (sort of) natural kind, the autopoietic theory understands them as constituting only a conventional kind. Additionally, the paper shows that AT’s conventionalist stance about cognition, far from being an undesirable or useless position, offers some methodological virtues that might be timely and welcome in the agitated and revolutionary climate of current cognitive science.