This paper presents an argument for the realism about mechanisms, contents, and vehicles of mental representation at both the personal and subpersonal levels, and showcases its role in instrumental rationality and proper cognitive functioning. By demonstrating how misrepresentation is necessary for learning from mistakes and explaining certain failures of action, we argue that fallible rational agents must have mental representations with causally relevant vehicles of content. Our argument contributes to ongoing discussions in philosophy of mind and cognitive science by challenging anti-realist views about the nature of mental representation, and by highlighting the importance of understanding how different agents can misrepresent in pursuit of their goals. While there are potential rebuttals to our claim, our opponents must explain how agents can be rational without having mental representations. This is because mental representation is grounded in rationality.the difference between human conceptual abilities and a frog's ability to detect when it has mistakenly targeted an object:Sometimes Macbeth starts at mere dagger appearances; but most of the time he startles only if there's a dagger. What Macbeth and I have in common-and what distinguishes our case from the frog's-is that though he and I both make mistakes, we are both in a position to recover. By contrast, frogs have no way at all of telling lies from beebees (Fodor 1992, p. 107).Fodor, however, did not extensively explore this idea. In contrast, Mark Bickhard has made error detection a criterion for the adequacy of any naturalistic approach to intentionality (Bickhard 1993(Bickhard , 2009. According to his account, error detection occurs in basic representations that drive the actions of an agent, provided the agent can recognize when anticipated actions fail. Therefore, the ability to detect failure is something that frogs may lack, at least in regard to things they snap at (if Fodor's assessment is correct), but it is a capability that we (and Macbeth) possess.Earlier attempts to underscore the importance of error-correction mechanisms in representational theories have provided a clear perspective on the causal role of content in