It is sometimes said that humans are unlike other animals in at least one crucial respect. We do not simply form beliefs, desires and other mental states, but are capable of caring about our mental states in a distinctive way. We can care about the justification of our beliefs, and about the desirability of our desires. This kind of observation is usually made in discussions of free will and moral responsibility. But it has profound consequences, or so I shall argue, for our conception of the very nature of beliefs and other mental states. Suitably developed, it allows us to draw a line between two distinct ways in which a creature may possess a belief, represent a scene, and fall into error. The first way (which I shall call the 'mindless' way) involves little more than an encoding of information in some way designed to guide appropriate response. This is the common heritage of humans, and many other animals. The second way (which I shall call the 'mindful' way) requires that the creature be capable in addition of a special kind of second-order reflection, and (importantly) be expert at detecting the kinds of situation in which such reflection is called for. The differences between these two ways of 'believing that P' are sufficiently deep and significant to warrant (or so I claim) our treating them as two distinct classes of mental states. For it is only courtesy of the second layer of complexity, I shall argue, that it becomes proper to hold someone accountable for their beliefs or other mental states, and it is this fact of (something like) accountability that in turn raises the most significant challenge for philosophical attempts to give naturalized accounts of meaning, belief, and mentality.