Many Christians claim to form justified beliefs based on a spiritual experience (e.g. the internal witness of the Holy Spirit) or a spiritual cognitive faculty (e.g. the sensus divinitatis). The skeptic retorts: ” Wait, how is this internal witness (or this sensus divinitatis) supposed to work?”
Now, this is a perfectly fair question. However, it is also perfectly fair for the Christian to reply, “I have no idea.”
The skeptic replies indignantly: “But how can you form justified beliefs from a spiritual experience or cognitive faculty if you don’t know how it works?” And I’ll reply in kind:
“I assume you have justified beliefs about your current bodily location. And you also have justified sense perceptual beliefs about your immediate environment. And you have justified beliefs based on your memory, and your rational intuition, and testimony. Do you know how proprioception, sense perception, memory, rational intuition, and the epistemology of testimony all function? Is that knowledge of cognitive function requisite for gaining justified beliefs from these various doxastic faculties? Surely not.”
“Hold on,” the skeptic says. “There’s a big difference between those universal, common, mundane faculties and your so-called internal witness of the Holy Spirit.”
“Is there?” I reply. “Let’s take the first example: proprioception. Many people suffer various degrees of proprioceptive malfunction. How widespread would that malfunction need to be before the person with a properly functioning proprioceptive capacity would be required to explain how it functions in order to be justified in accepting the deliverances of proprioception? And why is that threshold required? Who decides such things?”