This study examines Thomas Pynchon’s The Crying of Lot 49 through Peter Carruthers’ Interpretive Sensory-Access (ISA) Theory. ISA theory suggests that self-consciousness comes from interpreting sensory and contextual information rather than directly accessing thoughts. In ambiguous situations, this leads individuals to create confabulation—coherent but possibly inaccurate stories about their own mental states, explaining gaps in their self-knowledge. This study examines the fragmented and fluid identity of Oedipa Maas, the protagonist of Pynchon's novel, through her encounters with enigmatic signs like the “muted post horn” and W.A.S.T.E. postal system. Influenced by the cultural anxieties of the 1960s, her self-consciousness is shaped by reflective interpretations rooted in the era’s social and media contexts. Employing an interdisciplinary approach from philosophy of mind and literary criticism, the research uncovers Pynchon's deliberate portrayal of postmodern cognitive and narrative processes—characterized by fragmented, multilayered understandings of identity and narrative. This highlights the instability and multiplicity of identity driven by ambiguity and polysemy— the presence of multiple related meanings in a single sign— within the text. Moreover, the framework can be applicable to similar and realistic narratives, emphasizing Pynchon’s central role in exploring contemporary identity and consciousness and suggesting new directions for future scholarship in literature and philosophy of mind.