Criminal law is no longer the exclusive domain of national legislatures. International criminal law has established itself as a new field of law, and national penal legislation has become the object of European regulation. The science of criminal law, traditionally accustomed to think within the boundaries of national law, is now faced with new tasks of analysis and systematization. Since the use of national legal concepts will create confusion in the emerging international legal discourse, an attempt is made here to grasp the notions of criminal intent and mistake in a set of neutral analytical instruments as a precondition for a transnational doctrine of mens rea and the necessary comparative work. This includes an appraisal of the impact of analytical philosophy and cognitive psychology on criminal law doctrine.