For Ryan Long:
Grey suggests that this means that the value of knowledge is in its ability to predict the future; that we come to believe in the best estimator of reality thanks to its proven value as an estimator. He might even be right about that - but even if so, what does that have to do with truth or knowledge? Something isn't true because it serves as the best estimator, but the exact reverse: because something is true, it therefore serves as the best estimator.
While my writing on the subject hasn’t been particularly consistent, at least in regards to term usage, I would actually say that the value of knowledge is in its ability to recall the past. In contrast, it would be beliefs whose value is derived from its ability to predict the future (or the past, even). My main dichotomy is that of knowledge and beliefs. Knowledge is experiential in my worldview, and thus refers strictly to what one experiences directly for oneself. Belief is non-experiential, and refers to that which one experiences vicariously. Burning your hand on a hot stove is knowledge; being told that touching a stove will cause your hand to be burned is belief.
As such, beliefs aren’t true or false, per se, but rather more reliable or less reliable. Because something is more reliably replicable, it is more reliable. Really, there is no way to truly determine what is the best estimator of reality, but rather what is the most accurate estimator of reality within the context in which it is used.
More to the point, we can know personal truths for ourselves, but we can only really ever guess at external, universal truths. We can’t ever really know with perfect certainty how accurate our guesses are, but their practical functionality does serve as some sort of proof of their validity.
I trust that this clarifies rather than muddles. I use these terms in particular ways in order to elucidate the difference between knowledge and belief, and to show that certainty is not necessarily a by-product of knowledge. Honestly, this stems from my theological philosophizing, and happens to be useful in understanding science, epistemology, and even human behavior. The reason why most people act with certainty is not because they know a lot, but because they believe a lot. Thus, life is less certain than most people will admit.