This introduction establishes the foundational framework for examining mental representation in cognitive science and philosophy of mind. Through analysis of everyday practices and scientific research, it demonstrates the essential role of mental representations in explaining instrumental rationality, learning from errors, and adaptive behavior. The discussion reveals how representations enable both error detection and correction across different levels of cognitive sophistication. Two key meta-desiderata are introduced: (I) connection with empirical research and (II) explication of representational intentionality in scientific and everyday contexts. These generate specific requirements for an adequate theory of representation, including its role in description, explanation, and prediction; applicability across linguistic and non-linguistic phenomena; and manifestation at personal and subpersonal levels. Using three key examples from cognitive science—cognitive maps, mental imagery, and concept learning (rombix)—the introduction demonstrates how mental representations function in scientific practice while establishing criteria for evaluating competing theories. This analysis sets up the subsequent examination of internalist, externalist, and teleosemantic approaches to mental content, leading toward development of a novel coherence-based account of system-detectable error.