Some time back I have touched on the idea of Foundationalism. Foundationalism, or How to be Confused About Epistemology is a post by David Decosimo about the fear that some have that rejection of foundationalism leads to a rejection of turth. I found it very helpful. I even understood part of it.
As long as one thinks that people can be rational or justified in their believings and still be wrong, then one needs to get out of the business of being a foundationalist or fretting over the rejection of foundationalism. The rejection of foundationalism does not remotely commit one to relativism or skepticism with respect to truth. Nor does it mean that one needs to hold one's justified beliefs as though they were less than true.
Contrary to what the rhetoric of folks like Helm seems to imply, it would be difficult, if not impossible to find a Christian (or anyone!) who was a foundationalist for at least the first 1500 years after Christ's birth. Presumably most of these Christians were neither relativists nor skeptics, so it makes little sense to claim that the absence of foundationalism leads to those things. And Helm in particular, author of the book on Calvin that he is, should know that for Calvin belief in God is rational not because it can be founded on indubitable premises, but because a properly functioning "sense of the Divine" produces just such a belief.