 The term “fideism” appears to have entered the philosophical lexicon by way of theology in the late nineteenth century. It was originally used in reference to a movement within Roman Catholic thought, also known as traditionalism, which emphasized, over against rationalism, the role of tradition as the medium by means of which divine revelation is communicated, and which was sometimes conjoined with a conservative social and political agenda. Although of late modern vintage, the term “fideism” has since been applied retrospectively to thinkers at least as far back as the second century C.E.