The philosophical discourse on personal identity—the metaphysical question of what constitutes an individual's persistence through time—achieved significant rigor with the work of thinkers like Harold Noonan. His contributions, rooted in the analytic tradition, rightly compel an exhaustive inventory of the necessary and sufficient conditions for an individual's continued existence. One should reject any flippant or equivocal representation of such serious scholarly contributions.
I. Noonan's Criterion and the Limits of the Physical
Noonan's analysis primarily explores the sufficiency of physical and psychological continuity as criteria for identity.
A. The Physical Criterion (Bodily and Brain-Based)
Noonan's work engages critically with the Bodily Criterion, which posits that persistence requires physical continuity of the whole organism.
The thought experiment involving an individual claiming to Napoleon, possessing Napoleon's apparent memories, directly challenges this view. The individual's body remains distinct from Napoleon's body, indicating that body alone fails to as the definitive condition.
Noonan subsequently foregrounds the Brain Criterion: the identity of an individual at time with an individual at time depends on the physical continuity of the brain. This part most responsible for maintaining a consistent personal history. The success of a hypothetical brain transplant would, by this criterion, transfer the person, not merely an organ.
B. The Psychological Criterion (Lockean Continuity)
Noonan also draws upon John Locke's core insight: personal identity depends on the continuity of consciousness, primarily manifested by memory.
This forms the basis of the Psychological Criterion, which claims identity persists through the continuous connection of an individual's psychological states (memories, beliefs, habits, character traits) over time.
The persistence of habits and continuous character traits across different temporal phases underscores this aspect. The "I's union of character" resists immediate change when, for example, a person switches academic majors; the 'I' remains conceptually continuous, even as its descriptive reality changes.
II. Revision: Parthood, Temporal Entities, and the Multiplicity of Identity
One should consider Noonan's underlying assumption: the unitary nature of personal identity. A departure from this "Simple View" compels us to consider the implications of multiplicity and vague persistence.
A. The Challenge of Temporal Part-hood
The notion that we exist not as single entities but as a collection of temporal parts—distinct entities existing at different times—profoundly challenges the singular view.
If I remove a tumor, I excise a part that shared my physical composition yet failed to share my personal identity. Similarly, replacing a major organ (a heart transplant) fails to alter the core identity, suggesting that not all physical parts possess equal metaphysical weight.
The gruesome thought experiment concerning the self and severed limbs or a severed head highlights the cognitive bias toward a singular point of view. We instinctively locate the self either in the head (the site of consciousness) or in the whole body, but rarely consider the potential for multiple, distinct personal identities existing across different temporal moments.
B. The Logic of Parthood (Lego-hood)
The analogy of or 'Lego-hood' offers a precise way to model this complex structure. Personal identity molecular building blocks (particles) that undergo continuous replacement and reorganization.
The Ship of Theseus paradox aptly demonstrates the problem of persistence through change. If we replace all components, does the object retain its original identity? In the context of the self, if every particle and every memory changes over a lifetime, where exactly does the singular "I" reside?
The singular reference to personal mind versus personal body breaks down. composite, multi-part machines. Group identity and stereotyping mirror this error, treating a diverse collective of distinct individuals as a singular, undifferentiated entity, which further reinforces the societal illusion of singular identity.
C. Identity as a Trans-dimensional Process
Identity should constitute a single, static phenomenon but as an ever-changing process of manifesting temporal parts.
Behavioral and Cognitive Change: When a gender non-conformist transitions, the defiance more than just physical changes; it changes the social and psychological dimensions of identity through time. When one devours information (or alcohol), the contents of the brain change, reflecting a continuous revision of the self's reality.
The Unknowable Self: The persistence of identity becomes a lifelong assumption. Our core identity remains elusive, unknowable in the absolute sense, but its manifestations—the many varied temporal actions orchestrated over time—serve as the only documentable reality.
The final assertion remains: Personal identity constitutes a dynamic, evolving construction, much like a choose-your-own-ending book. No single, universal criterion will capture the complexity of all individuals, whose distinct temporal parts continually redefine the within a framework of ever-changing existence.
Do the implications of this temporal part-hood thesis compromise the ethical foundation of moral responsibility? If no single, unitary 'I' persists, who should we hold accountable for past actions?






