There’s an idea that there are certain questions that must be answered in order for any other questions to be asked and answered, but this is mistaken. There certainly are questions we can ask where our answers must be assumed true, but examining whether or not this effects any other enterprise of inquiry is actually very doubtful.
Rather than suppose the answer is “I do exist.” to the question, “Do I exist?”, what if I simply throw it out for being a nonsense question?
We can actually color all “cornerstone” or “properly basic” beliefs in such a way and all that changes is perspective, not how we go about justifying what we think some state of affairs is. So while Descartes may have been keenly interested in that sort of question, a Pragmatist or Linguist may simply say that what “I” and “exist” mean does more, or actually does all of the work in settling the importance of the question because it isn’t the fact of being a brain in a vat that’s of import. We cannot answer that question. But whether we are or are not doesn’t change either our concepts of “I” or “exist”; the experience is identical and so other questions like vats for brains or “really real realities” is immediately apparent as a dim question, an unnecessary one.
But, it’s the kind of question which demonstrates the lack of a need of concepts like “properly basic” beliefs or “cornerstone” propositions. In fact, the only sense in which they matter to epistemology is if we mandate, by fiat, that they must be a part of our paradigm of thought. In fact, they mustn’t.
This entire way of thinking is merely the remnant artifact of Descartes’ once dream of reduction and reconstruction. While he utterly failed in his attempts to reduce, as plenty of Analytic Philosophers have weighed in heavily by now, René failed to reconstruct even with the most forgiving compatriot of thought as sympathetic judges.
We do not begin with doubt and that we can doubt is no justification to doubt and all moves in Epistemology require justification, including doubting beliefs which we have arrived at simply by compelling pursuation of some states being obviously so. If we encounter such a question whose answer is so impossibly something else, we are justified in claiming we’re entitled to it until such a time as justified, reasonable doubts can be raised.
But given no question necessarily must be addressed, we avert a regress of “Well, why?” to every conclusion we have come to. In short, justification has never hinged on our ability to answer all questions we could ever ask. And given we in fact have quite a few justified beliefs, and a universe of unasked mysteries, the “problem” of “cornerstone” or “properly basic” beliefs is simply that they are thought to actually be genuine and mandatory when what they are is an artifact from a failed hope of a long-dead French philosopher.
Just a thought.