John Locke’s theory of personal identity, as articulated in An Essay Concerning Human Understanding, posits that continuity of consciousness is essential for personal identity over time. For Locke, consciousness primarily involves memory of past experiences. As such, this essay examines Locke’s theory, evaluates its strengths and limitations, and argues that consciousness alone is insufficient to fully account for identity. It begins by examining why Locke thinks psychological continuity is essential to identity.
Locke defines a person as a “thinking intelligent being” capable of self-reflection and of recognising itself as the same entity across time.1 In contrast to theories tying identity to the body or soul, Locke argues that identity is rooted in psychological continuity, specifically memory of past actions and thoughts. He supports this with the famous thought experiment—the prince and the cobbler. In this thought experiment, the prince’s consciousness, including his memories, inhabits the cobbler’s body and vice versa. Because the prince retains his memories and self-awareness in the cobbler’s body, he remains the prince, showing that identity is tied to consciousness, not the physical form or social relationships.2 Here, Locke’s theory aligns with our intuitive sense of self, where memory links past and present, rather than bodily features or social roles. Yet, despite its intuitive appeal, Locke’s reliance on memory as the sole criterion for identity invites significant philosophical challenges.
Locke’s memory-based theory of personal identity faces key challenges of circularity and logical inconsistency. Joseph Butler argues that Locke’s theory is circular: memory presupposes an existing self who recalls experiences, so it cannot define identity.3 If identity depends on memory, but memory already assumes a self to do the remembering, Locke’s definition becomes circular and fails to establish identity independently. Thomas Reid’s “Brave Officer” paradox further challenges Locke: a boy (A) flogged at school becomes an officer (B) recalling the flogging, then a general (C) remembering B but not A. Per Locke’s theory, A = B, and B = C, but C ≠ A. However, this violates identity’s transitivity such that if A = B, and B = C, then it must follow that C = A.4 Building on the critiques of Locke’s theory, the challenges posed by amnesia further expose the incompleteness of his framework.
Amnesic patients who lose significant portions of autobiographical memory are still recognised as the same person legally, socially, and morally. This persistence of self, grounded in physical and social continuity, demonstrates that memory alone cannot account for personal identity. Even when psychological continuity is severed, the individual’s obligations, traits and relational history remain, indicating that identity transcends remembered content. Any robust theory of identity must therefore supplement psychological continuity with factors such as physical or social continuity to account for cases of memory loss.
In summary, this essay examined Locke’s argument, evaluated its strengths and limitations, and argued that consciousness alone is insufficient to robustly account for identity. While Locke’s emphasis on the sameness of consciousness provides a compelling psychological foundation of personal identity, its circularity, logical inconsistencies, and failure in cases like amnesia suggest memory alone cannot fully explain identity. Though influential, Locke’s theory needs refinement to address the complexities of personal identity.