  Here is one line of thought for the conclusion that a sufficient level of nonculpable error about one's environment does tend to compromise one's ability to arrive at rational beliefs about that environment. It's plausible to suppose that much if not all of the value that we place on believing rationally depends on a connection between believing rationally and believing what is true (although the precise nature of this connection is no doubt a particularly vexing topic). One might worry that a view according to which even ideal, perfect rationality can coexist harmoniously with a more or less completely mistaken view of one's situation threatens to attenuate the connection between believing rationally and believing truly too far, and to render obscure why the former would be valuable relative to the latter. To put the same point in terms of evidence: plausibly, much if not all of the value of respecting one's evidence consists in the putative link between doing so and believing the truth. Given this, one might worry that a view according to which perfectly following one's evidence is compatible with a more or less completely mistaken view of one's situation threatens to render obscure why following one's evidence would be a good thing to do relative to the goal of having true rather than false beliefs.