A Christian believes in heaven, hell, and the resurrection of Jesus on faith. A Muslim rejects the resurrection but accepts Muhammad as the true prophet on faith. A Hindu rejects both Christianity and Islam but believes in karma and reincarnation on faith. And so on.
According to SEP, Fideism is:
“Fideism” is the name given to that school of thought – to which Tertullian himself is frequently said to have subscribed – which answers that faith is in some sense independent of, if not outright adversarial toward, reason. In contrast to the more rationalistic tradition of natural theology, with its arguments for the existence of God, fideism holds – or at any rate appears to hold (more on this caveat shortly) – that reason is unnecessary and inappropriate for the exercise and justification of religious belief. The term itself derives from fides, the Latin word for faith, and can be rendered literally as faith-ism. “Fideism” is thus to be understood not as a synonym for “religious belief,” but as denoting a particular philosophical account of faith’s appropriate jurisdiction vis-a-vis that of reason.
1. A Formal Definition
Alvin Plantinga has noted that fideism can be defined as an “exclusive or basic reliance upon faith alone, accompanied by a consequent disparagement of reason and utilized especially in the pursuit of philosophical or religious truth” (87). Correspondingly, Plantinga writes, a fideist is someone who “urges reliance on faith rather than reason, in matters philosophical and religious” and who “may go on to disparage and denigrate reason” (87). Notice, first, that what the fideist seeks, according to this account, is truth. Fideism claims that truths of a certain kind can be grasped only by foregoing rational inquiry and relying solely on faith. Insofar as fideism insists that knowledge of these truths is possible, it must be distinguished from various forms of skepticism with which it otherwise shares certain common features. Notice too that this definition is largely formal; the plausibility of fideism as a philosophical doctrine and the proper extension of the term will therefore depend on the content given to the terms “faith” and “reason.”
How can faith, or fideism, be considered a sound epistemology in the pursuit of truth if mutually exclusive beliefs can be equally "justified" through faith?
How does Alvin Plantinga define faith?
Plantinga's account of faith gives us a good clue I think as to why he would gravitate toward a picture according to which Christian beliefs are properly basic. Following Calvin, Plantinga defines faith (or faith of the type he wishes to discuss) as a "firm and certain knowledge" of "the central teachings of the gospel" (pp. 244-249). This certain knowledge is not arrived at by the workings of any of the faculties we were created with, but is the result of the work of the Holy Spirit (p. 245), who "causes us to believe these great truths of the gospel" (p. 245). Let "Plantinga faith" be faith as Plantinga describes it, leaving out the part about the beliefs in question constituting knowledge. (I want to identify "Plantinga faith" in a non-evaluative way in order to leave as an open question the status of beliefs that are the result of "Plantinga faith.") Plantinga faith then is a very strongly held belief in the great truths of the gospel, produced in accordance with God's plan by the Holy Spirit in the way Plantinga describes. How strongly held? Very strongly: It is a "firm and certain" belief (p. 244), one finds the beliefs so caused to be "compelling" (p. 250). Would the fortunate recipient of Plantinga faith have properly basic beliefs? Even after reading Plantinga's defense, I don't find this matter nearly as clear as Plantinga seems to find it, but it does seem plausible to me to suppose so.
Quoted from: https://www.baylor.edu/content/services/document.php/40620.pdf
