Here's an excerpt of a conversation I just had with a Clarkian:
[Marc] If any other propositions outside the Bible are just guesses, then how do you know you're reading this?
I don't know, but I have a pretty strong opinion that I am.
[Marc] How do you know you're reading the Bible?
I don't. God reveals His truth to His people directly, apart from sensations.
[Marc] How do you know that the actual words on the pieces of paper in what you call your "Bible" are the actual Bible?
[Marc] How do you know that God revealed truth to you through Gordon Clark's writings if you don't know that Gordon Clark even existed?
God helps His children understand Him better in mysterious ways. (What He has
shown me through Clark here is in logical concord with His Word.)
[Marc] How can you make a judgment about the spiritual state of anyone if you do not even know they exist?
I can have an educated opinion about it, but not knowledge. Opinion is
sufficient for making decisions like this. In think most of daily life's
decisions are based on opinions and it seems to work out reasonably well for
most. Of course, opinion does not get you into heaven and this is where
knowledge is essential, i.e. the intellectual understanding of and assent to the propositions that constitute the gospel.
[Marc] How do you know you presented at Robbins's forum? How do you know that Robbins and his disciples ignored or rejected what you said? How do you know you were listening to Gordon Clark on tape? How do you know that this is what Gordon Clark believed about knowledge?
Again, opinions here are sufficient for me. As I am made aware of the various
propositions attributed to a man named Gordon Clark, I test these against the
revealed propositions in the Bible. If they withstand the logical test, I
regard them as truth even though I can only opine about the existence of G.
Clark and that he was the author.
[Marc] How do you know that the gospel you believe is the one in the true Bible, which you may or may not have? How do you know you're not dreaming or hallucinating all of this?
[Clarkian] Surely you are familiar with Descartes' ultimate proof "cogito ergo sum", with which I disagree because it is based on Rationalism which seems to be in conflict with Scripture. To answer you when you ask here how I know that I am not dreaming or hallucinating about the truth: CREDO ERGO SUM! Only believers know, i.e. understand and assent to the truth, the propositions of the Bible, Jesus Christ. I cannot know that I am not dreaming or hallucinating about non-Bible+necessary inference propositions, and neither can you, IMO.