First Published in 1998. This is Volume XI of twenty-two in a series on Social Theory and Methodology. Notions are widespread that sociological theory is either an industrious activity on the drawing boards of the architects of fantasy or a branch of esoterics operating in a shadowy realm of semi-darkness. The present study holds neither of these conceptions of sociological. The present study’s function is to illuminate the difference between one theory and another. The power and reliability of a theory are not always evident all at once. A theory may have a power to explain what was not originally anticipated; it may also disclose the existence of problems it cannot explain.