"Nothing is in the intellect that was not first in the senses" - Thomas Aquinas
This statement from Thomas Aquinas, known as the peripatetic axiom, expresses the basis of empiricism, and was adopted from Aristotle's teachings. It became part of his Thomistic philosophy. But Aquinas had a religious agenda. He needed to justify his belief in something (namely God) that doesn't present itself to the senses. So as he did with other parts of Aristotle's teachings, he modified it to fit his religious purpose. Aquinas said that the intellect extends beyond what is evident to the senses, to reach a higher realm of understanding that is yet justified on the basis of perception. His five ways are said to be a posteriori arguments for the existence of God because they are based on observation (as well as a system of metaphysics that assumes God from the outset). So at least Aquinas pays lip service to the idea that knowledge of God is something that is derived from from the evidence of the senses.
Perhaps it was because there was a recognition that Aquinas employed something more than observed evidence to derive his proofs of God, it has become more fashionable in modern times for religionists to rely more heavily on a priori knowledge as an epistemological basis for their belief. In general, a priori refers to things that are known without reference to sensory experience - they are known beforehand, through intuition or by deductive process rather than empirical observation. This concept has been extended further by religionists to refer specifically to knowledge of God by other than empirical means. In particular, the term "Religious A Priori" has been deemed to mean a rational and certain knowledge of God based on subjective religious experience.
Religious A Priori: A separate, innate category of the human consciousness, religious in that it issues certain insights and indisputable certainties concerning God or a Superhuman Presence. Man's religious nature rests upon the peculiar character of his mind. He possesses a native apprehension of the Divine. God's existence is guaranteed as an axiomatic truth. For Ernst Troeltsch (1865-1923) this a priori quality of the mind is both a rational intuition and an immediate experience. God is present as a real fact both rationally and empirically. - Runes Dictionary of PhilosophyThis is taken to the extreme by Joe Hinman, who not only justifies his belief on the basis of religious experience, but also exempts his belief from any examination or critique from an empiricist perspective - or from any scientific or philosophical discipline whatsoever. One of his numerous blogs is dedicated to the religious a priori. The main page explains his religious epistemology, and presents an "argument" that comes across as more of a manifesto, wherein he both rejects empiricism and walls his beliefs off from any and all scrutiny:
(1) Scineitifc reductionism loses phenomena by re-defining the nature of sense data and quailia.Basically, Joe is saying his beliefs are based on nothing more than subjective feelings, and so he rejects empiricism, as well as any scientific or logical approach to justifying those beliefs or to challenging them. Which is strange, given that Joe has written a book that purports to provide scientific evidence that belief in God is warranted. Just don't try to pin him down on any technicality in his arguments, because he will simply revert to the epistemological isolationism expressed in his manifesto: I argue from a priori knowledge and there's no way you or anybody can possibly argue against that.
(2)There are other ways of Knowing than scinetific induction
(3) Religious truth is apprehended phenomenoloigcally, thus religion is not a scientific issue and cannot be subjected to a materialist critque
(4) Religion is not derived from other disciplines or endeavors but is a approch to understanding in its own right
Therefore, religious belief is justified on its own terms and not according to the dictates or other disciplines
This a priori stance even takes precedence over logic itself. When I accused him of begging the question in one of his arguments by assuming the conclusion up front, his response was this:
we are talking about God a priori so it can't be begging the question that is really foolish reasoning,makes me wonder if you understand begging the question - HinmanIn other words, by claiming this a priori stance, Joe is immune from even the need to present a valid argument. If you try to tell him his argument isn't valid, you're the one who doesn't understand logic. And this is what I call the A Priori Gambit. It's a sure-fire way to win all arguments. Perhaps I should try the same tactic. But no. I don't think it impresses much of anybody so much as it impresses Joe.