Nineteenth-century biblical critics "thought of themselves as continuing the aims of the Protestant Reformation". According to Robert M. Grant and David Tracy, "One of the most striking features of the development of biblical interpretation during the nineteenth century was the way in which philosophical presuppositions implicitly guided it". Michael Joseph Brown points out that biblical criticism operated according to principles grounded in a distinctively European rationalism. By the end of the nineteenth century, these principles were recognized by Ernst Troeltsch in an essay, "Historical and Dogmatic Method in Theology," where he described three principles of biblical criticism: methodological doubt (a way of searching for certainty by doubting everything); analogy (the idea that we understand the past by relating it to our present); and mutual inter-dependence (every event is related to events that proceeded it).