This paper strengthens Bhaskar's case for the possibility of naturalism. Building on Bhaskar's A Realist Theory of Science and The Possibility of Naturalism, and on more recent contributions by Douglas Porpora, it traces the evolution of Bhaskar's concept of 'intransitive' and follows his suggestion to treat social structure as an intransitive generative mechanism analogous to the generative mechanisms of the natural sciences. It is suggested, building on Porpora, that the constitutive rules of the market are usefully regarded as generating an intransitive 'basic social structure.' That this same intransitive object is reasonably regarded as continuing to exist and act under different descriptions is illustrated by citing how different scholars have approached it with different concepts and vocabularies. It expands on Bhaskar's first example of an intransitive object of social science, the mass unemployment that provided a motor' for Keynes, and on Porpora's examples of the causal powers of social structures.