I withheld commenting on this post by Dick until Mike had his chance.
Those labels can (conceptually) be divided into two sets: the things we know and the things we think we know. Here I regard the "things we know" as that set of things which god himself would agree were things correctly known by us. Or better yet, things a scientist a million years from now would agree were correctly known by us. Or maybe even better than that, those things about which you will never change your mind no matter how long you wait. Or perhaps those things that you didn't change your mind about when you discovered that error in your beliefs (the last error you discovered). Of course, if you have never discovered an error in your beliefs, you have no need to talk to me as you clearly know all there is to know... Consider the problem as seen by god himself: he knows exactly what you think you know which is wrong and what you think you know which is correct. Or better yet, that scientist a million years from now who could point out many things you think you know which are wrong and what you think you know which is correct. Or maybe even better than that, the things you think you know which you think are correct and the thing you have just discovered which you thought you knew but which turned out to be wrong. These two categories are what I refer to as "knowable data" (that which you think you know which is correct) and "unknowable data" (that which you think you know which is not correct). "Correct" here being defined any way you wish consistent with the discussion in the three previous paragraphs.
Here is a clear confusion on Dick's part. He tries his best to distinguish 'knowable' and 'unknowable' data by defining these two sets of data, but is this distinction an ontic distinction or an epistemic distinction?
If ontic distinction, then his model is an ontological model, or if it is an epistemic distinction, then it is an epistemological model. Notice the conflict he has in the post above. He first offers an ontic distinction ("that set of things which god himself would agree were things correctly known by us"), and then unsatisfied and foreseeing the problem here, he tries to introduce an epistemic distinction ("Or perhaps those things that you didn't change your mind about when you discovered that error in your beliefs (the last error you discovered)"). The former is a distinction that is entirely metaphysical. There is no way we could know what God absolutely thinks since even if God were to let himself be known and came forward with what he knew, in the same vein God could tell us something that he later could say we misunderstood, or he simply doesn't tell us information that led to us drawing the wrong conclusion, etc. The point being that this is an ontic distinction of 'knowable' data which Dick himself doesn't see as the best distinction by how to present his model.
But, if we ignore his ontic stray, and look at his epistemological distinction ("Or perhaps those things that you didn't change your mind about when you discovered that error in your beliefs (the last error you discovered)"), then we see that this is not strong enough to guarantee that you actually have knowable data. It is all too easy to believe something that is false even if you never discover your error. For example, we might form a belief of what gravitational forces lurk inside a blackhole, and according to theory and indirect evidence, we feel that we 'know' this theory to provide an accurate understanding (knowledge) of what is happening inside a blackhole. However, we are prevented from going inside a blackhole by the forces of preventing us to return the correct state of affairs, and therefore our theory has unobservable data that is believed to be 'known'. If Dick's epistemic distinction is correct (i.e.,
"Or perhaps those things that you didn't change your mind about when you discovered that error in your beliefs (the last error you discovered)"), then our unobserved but believed-to-be-true beliefs about the inside of blackholes is actually 'known data'. However, this is not 'known data' since conceptually it could be wrong. Our last standing theory of inside blackholes could be wrong, and only the data - which we cannot access - would prove that we were wrong. Hence, in using only an epistemic distinction, Dick's model fails since his 'known data' might actually be 'unknown data'.
This leaves Dick only with an ontological recourse, but this is does irreputable damage to his model since he takes an epistemic approach to justify his model (i.e., "The first thought which should arise in your mind is 'how does one come to know that something they thought they knew was actually wrong?' It should be clear that this happens whenever one becomes aware of an inconsistency in what they think they know."). Notice that Dick approaches the matter of knowledge epistemologically ('the first thought which should arise'), but depends on ontology (e.g., god himself) to establish his designations!
If Dick were to offer a purely ontological model, then he could claim no certainty, but he wants certainty in his model (i.e., as much certainty as mathematics can provide), so that's why he pursues the epistemological route. Unfortunately for him, his epistemological route depends on an ontic distinction, which means that he can never achieve any epistemological degree of certainty but is only as certain as his ontology will allow. If his ontology is wrong (e.g., there is no such knowable and unknowable data but all data is simply pragmatic data - for human use only having neither 'true' or 'false' properties), then Dick has made poor assumptions and his model is entirely wrong.
Now, that's not so bad to be wrong, people are wrong all the time. The trouble is that Dick's approach is epistemic and if it is danger of being wrong, then this means he has taken an invalid approach to establish our degree of certainty with regard to science. Since he cannot show that a purely epistemic approach is any more valid than an epistemic/pragmatic approach such as science, then this gives us no other recourse but to establish our scientific knowledge based on the success of science (e.g., sensibility that science offers, etc). Dick has failed in his attempt to find a foundation to scientific knowledge, and therefore his model must be cast aside as a mere curiosity.
Warm regards, Harv