Fideism () is an epistemological theory which maintains that faith is independent of reason, or that reason and faith are hostile to each other and faith is superior at arriving at particular truths (see natural theology). The word fideism comes from fides, the Latin word for faith, and literally means "faith-ism". Philosophers have identified a number of different forms of fideism.
Theologians and philosophers have responded in various ways to the place of faith and reason in determining the truth of metaphysical ideas, morality, and religious beliefs. A fideist is one who argues for fideism. Historically, fideism is most commonly ascribed to four philosophers: Blaise Pascal, Søren Kierkegaard, William James, and Ludwig Wittgenstein; with fideism being a label applied in a negative sense by their opponents, but which is not always supported by their own ideas and works or followers. A qualified form of fideism is sometimes attributed to Immanuel Kant’s famous suggestion that we must “deny knowledge in order to make room for faith”.