The Reformed Epistemology movement has constructed an elaborate explanation of how they think God beliefs are justified. In short, RE believers claim to have a direct immediate access to God through a witness of the holy spirit, religious experience, or sensus divinitatus. What’s important about this new source of knowledge is that it is private, it cannot be refuted by any contrary evidence, indeed, it rejects evidence altogether. This path to God is direct and veridical—without mistakes or confusions.
Here it is in William Lane Craig’s words:
Plantinga's model involves crucially what is usually called the inner witness of the Holy Spirit. In his model the Holy Spirit functions on the analogy of a cognitive faculty, producing beliefs in us. I myself prefer to think of the Spirit's witness either as a form of literal testimony or else as part of the experiential circumstances which serve to ground belief in God and the great truths of the Gospel. In either case His deliverances are properly basic. By that I mean that the experience of the Holy Spirit is veridical and unmistakable (though not necessarily irresistible or indubitable) for him who has it; that such a person does not need supplementary arguments or evidence in order to know and to know with confidence that he is in fact experiencing the Spirit of God; that such experience does not function in this case as a premise in any argument from religious experience to God, but rather is the immediate experiencing of God himself; that in certain contexts the experience of the Holy Spirit will imply the apprehension of certain truths of the Christian religion, such as "God exists," "I am condemned by God," "I am reconciled to God," "Christ lives in me," and so forth; that such an experience provides one not only with a subjective assurance of Christianity's truth, but with objective knowledge of that truth; and that arguments and evidence incompatible with that truth are overwhelmed by the experience of the Holy Spirit for him who attends fully to it.
After they argued that classical foundationalism was dead because it couldn’t how its basic principles were known: “Only those beliefs that we apprehend clearly and distinctly are true.” itself was challenged. Is knowing that principle itself something we apprehend clearly and distinctly? Or through justification? The idea behind RE was that we could apprehend more things directly and know them than just Descartes list of internal thoughts. When I see a flower, I am immediately aware of its title, and of its beauty. When it appears to me that the person I am talking to is angry, that’s something I know without any inference or reasoning. I know it directly and immediately.
How is it that they come to the confident conclusion that the deliverances of the holy spirit are veridical, objective knowledge? Because of features of the experiences themselves. The testimony of the Holy Spirit confronts them directly and does not misled them, they say. And the experience itself is so powerful, it eclipses whatever power to raise doubts some other ideas might have had. This internal source of knowledge of God gives the believer perfect assurance that any possible defeater that comes up is mistaken.
The RE development represents a retreat away from classic attempts to prove God’s existence on independent, non-circular, inter-subjectively verifiable grounds. The Holy Spirit has given this Christian the perfect answer to everything. The voices are internal and private. But what they instruct is without any doubt because the feelings are intense and authentic and unmistakable feeling. And the feelings give me perfect unassailable assurance that no matter what sort of counter evidence I encounter, it must be wrong. I have an internal, self-authenticating source of knowledge that cannot be mistaken.
There are a lot of objections to make to this sort of view. First, presumably even the RE adherent would admit that not all of the strong, passionate feelings like this that people have are authentic, even some of the ones where the subject is convinced that the experience is real, veridical, and religiously significant. They must be willing to admit that there are some false religious experiences that feel similarly compelling. If not, then they’d have to accept that all of the powerful, spiritual experiences that people have had count equally as objective knowledge. The problem is that too many people have had too many experiences like this that produce beliefs that are blatantly contradictory. They can’t all be correct. And surely the RE advocate wants to have some ground from which to argue that the Zoroastrians and the Palugans are wrong when they directly experience their gods. So the question is how does one tell the difference between the authentic visions and the bogus ones? Especially if the bogus ones are insisting that there’s are authentic just as vigorously.
Second, how can any mere feeling inside one’s own head be sufficient to give you a defeater for any possible counter evidence that comes along? Mere feelings in the head that are not manifest as objects in the world are notoriously subjective and unreliable. You can’t trust your strong feelings to tell you the truth about the world. And the only way we’ve ever had to check those feelings is to go look and confirm or disconfirm whether it was there. Cross-checking outside the voices in the my head, especially with other observers are the only or at least the best method we’ve ever had for separating the true from the false. It’s patently contrary to a thousand lessons every one of us has learned the hard way in our daily lives where the thing that felt sooo right in our minds turned out to be completely off the mark.
Third, consider the bigger picture here. There are millions of Christians and born-again evangelical Christians in the United States who wield enormous political, social, and economic power. They battle to set our school agendas, they put politicians into office, they vote for social agendas, and they propagate their ideas to the next generation of Americans. And here we are being told that ultimately the source of justification they have for their entire ideology is a set of intense, undeniable feelings they have in their minds. Furthermore, these ideas cannot be challenged (or even experienced) by anyone on the outside. In principle, they cannot be defeated because the feelings themselves inform the feeler that nothing else is so true or trustworthy.
The problem, obviously, is that the ideology has co-opted the RE’s capacity to think straight. Their dedication to the ideology has eclipsed all other concerns, even the person’s capacity to reason. Once someone is this far gone, the rest of us can only hope that the voices in their heads don’t start telling them to strap on a dynamite backpack or try to hasten the apocalypse by instigating World War 3.