Suppose you are tempted to agree with Lewis et. al. that knowledge doesn’t imply belief. Lewis’s example is of a timid student, uncertain of a given claim who will only hesitatingly answer, but answers correctly nonetheless. Not the most persuasive example: belief is compatible with some level of uncertainty, and it isn’t clear that the student knows that, e.g., Lincoln was assassinated in 1865.
Here’s a more interesting worry, however. Suppose Lewis is adamant about the example or some suitable refinement of it: the student knows the answer, and thus has propositional knowledge of some sort; and the student doesn’t believe the claim in question because he takes himself to be guessing (again, not a compelling inference, but I’ll let it go). Given such a position, true belief has something going for it in terms of a connection to action that knowledge doesn’t. To use Socrates’s example, you’re better off hiring a guide with true opinion about how to get to Larissa than hiring one with knowledge when that knowledge isn’t accompanied by belief. For, as in Lewis’s student example, we can expect hesitation and indecision from those who know but lack belief, and we have no such similar expectation concerning those with true belief. In fact, in the student case, if Lewis is right, the student might know and simply refuse to answer at all because of the lack of belief. The analogue in Socrates’s example would be a knowledgeable guide who won’t go any further at some point on the journey because he is uncertain which way to go. So, if you agree with Lewis, it looks like you should downplay the idea that knowledge is better than true opinion. Meno wondered why we prize knowledge over true opinion. If Lewis is right, such puzzlement is a confusion–the only general truth in the area is that when practical affairs are in view, true belief is preferable to knowledge. Sometimes knowledge is just as good as true belief, but in other cases it is not as good.
That implication strikes me as a mark against Lewis’s claim, though of course not a conclusive one.