Quick one. There aren't a ton of folks who identify justified belief with knowledge, but I think the number is increasing. At the very least, an increasing number are defending views that seem to carry the consequence that K = JB.
Case in point, consider this passage from Hawthorne and Stanley's, "Knowledge and Action":
Note that an analogous principle seems plausible for reasons for belief, viz: Treat
the proposition that p as a reason for believing q only if one knows that p. One attractive feature of the Action-Knowledge Principle is that it unifies the practical and theoretical domain of reasons: if it is correct, then proper reasons for belief and reasons for action have a uniform nature.
The argument. If a condition necessary for justified belief that p is true is that p is a reason for believing that which is an obvious consequence of it (i.e., justification is closed under known entailment), it would follow that Hawthorne and Stanley are thus committed to the view that knowledge of p’s truth is necessary for having a justified belief that p. After all, p is as obvious a consequence of p as any could be. Is that right?
That might have been a tad terse. The crucial assumption is this:
JC: If S's belief that p is justified, p is a reason for S to believe that which is an obvious (i.e., known with certainty) consequence of p.
This justification closure principle, (JC), gets us JBp --> Kp as follows:
(1) If p is an epistemic reason of S's, S knows p (H&S's view).
(2) If S's belief that p is justified, p is a reason for S to believe that which is an obvious consequence of p (JC).
(3) p is as obvious a consequence of p as anything is (DUH).
(4) If S's belief that p is justified, p is an epistemic reason of S's ((2), (3)).
(C) If S's belief that p is justified, S knows p((1), (4)).
That should be better.