This chapter analyzes internalist approaches to mental representation, focusing on narrow content and its theoretical limitations. Through examination of Fodor’s methodological solipsism and related theories, it demonstrates that internalist accounts either result in semantic ambiguity or strip mental representations of essential content properties. The analysis shows that attempts to characterize content purely through internal properties of cognitive systems fail to adequately account for reference and truth conditions. The chapter systematically evaluates key arguments for narrow content, including the ability to think about non-existent objects and context-independent thought. Through analysis of Searle’s Chinese Room argument, Harnad’s symbol grounding problem, and examples from cognitive science like rat navigation, it reveals how purely formal or syntactic approaches cannot capture the semantic properties necessary for genuine representation. The discussion establishes that single-factor internalist theories cannot satisfy core requirements for an adequate theory of mental representation, including the ability to account for representational error and the relationship between representations and their referents. This critique sets the foundation for examining externalist approaches to mental content in subsequent chapters.