The object of this paper is to elaborate an understanding of Islamic law and legal theory in terms of the conceptual framework provided by Legal Positivism. The study is not based on denying or contesting the claim of Islamic law to being of divine origin; rather, it is based on the historical reality of Islamic law as part of a (once) living legal tradition, with structure, method, and theory, regardless of claims of origin. It will be suggested that Ash'arism may be taken as providing an Islamic version of Legal Positivism, and that the objections which Mu'tazilism raised in the face of Ash'arism were not different in substance from some of the objections that have been directed at contemporary Legal Positivism. It will also be suggested that the Ash'arites and the Mu'tazilites were not opposed to each other in the way they are commonly supposed to have been. Rather, they were preoccupied with different notions of what it is to be obliged (to have an obligation) to do something.