The Natural Law and Thomas Aquinas’s Debt to Maimonides

Abstract: The natural law, which many take to be a constant presence in Catholic moral theology, was not of much interest to moral theologians in the twelfth century. Treatises on the moral life dealt mostly with the virtues, the Ten Commandments, and the gifts of the Holy Spirit. Considerations of the natural law were of interest primarily to canon lawyers. It was not until the thirteenth century that considerations on the natural law began to find their way into the works of theologians. What changed? I argue that it was the remarkable popularity of the third book of Maimonides’s Guide for the Perplexed , in which he attempted to provide rational explanations for what have seemed to many, both then and now, to be rather odd, somewhat arbitrary precepts in the Mosaic Law. This discussion in the Guide was made popular by prominent figures such as William of Auvergne and John de la Rochelle, and it inspired theologians such as Thomas Aquinas to consider more seriously how the precepts of the Old Law could be reconsidered in the light of the natural law tradition. Hence, we find in the Summa theologiae a rather short discussion of the natural law which is prefatory to a much longer discussions of the Old Law and the New Law.