This paper discusses the concept of human (social) action. It attempts to explain the relation between physical (observable) aspects of human action, and those aspects which are commonly believed not to be amenable to naturalistic explanation, such as thought, meaning, intention and symbolism. In other words, this is an attempt to understand the relationship between what is "internal" and what is "external" in, or about, action. The discussion has a broader philosophical significance inasmuch as it seeks to cast doubt on such dichotomies as nature and society, behaviourism and interpretivism, and the idea that nature and society requires different methods of study.