Introduction
Few human experiences are as universal as identifying with a self. No rational analysis is necessary to perceive it. It is considered a self-evident truth. Yet, questions on the nature of the self and whether it even exists at all have fueled debates for centuries. The limits of the physical body act as a natural demarcation between what most call the self and the rest of nature. Not only do such practical definitions aid self-preservation but also form the functional unit of society. Both rational and sometimes irrational behaviours such as love, altruism, or envy all happen within and to individuals who are their distinct selves.
What seems utterly obvious starts to be elusive under examination. If the body defines the self, does an individual losing their limbs lose themselves? At least partially? How about those who’ve had a stroke and can no longer communicate? Does a newborn, dependent on others have less of a self than independent adults? When the independent adults lose their agency to dementia, does their self remain?
A simpler approach may be to look for the self within oneself before extending to others. Little remains the same between being a teenager and raising one. Desires, hopes, disappointments, friendships could not be more different but what about the visceral feeling of identifying with oneself? The continuity of felt experience seems to point toward an enduring self, yet the closer we look, the harder it is to locate. The question is not merely philosophical, it is existential. How we understand the self shapes our approach to suffering, identity, loss, and change. It influences ethics, jurisprudence, end-of-life care, and our care of those whose minds have been altered.
Twenty-five centuries ago, a contemplative in India approached these questions with unparalleled rigor. His answer, anattā, challenges not just philosophical assumptions but the basis of how we experience being alive. We move the wheel of understanding forward by tracing a path from the evolution of our brains, the cognitive spurts that made self-reflection possible, to an analysis of experience itself.
Evolutionary history of the self
The emergence of Homo erectus approximately 1.9 million years ago marked the first significant brain expansion in our lineage. Cranial capacity increased to ~900cc from ~600cc in Homo habilis. Much of this expansion occurred in motor cortex, prefrontal regions, and areas integrating planning with execution.
Walking on two feet freed the hands and elevated the head, expanding visual range for foraging efficiently across the savanna landscapes. Bipedalism could emerge from a refined autonmic nervous system that evolved through vertebrates to adapt to the changing environment. The autonomic nervous sytem and the endocrine systems thankfully do not need volutary control during a fight or flight.
Abstract thought emerged alongside the neural networks that optimized survival of the species. The most useful thoughts were naturaly selected.
But the feedback loop between upright posture, expanded foraging range, tool use, and brain development create a selection pressure for sophisticated motor-cognitive integration. H. erectus were the first hominins to leave Africa, to create Acheulean hand axes requiring complex sequential motor patterns, and likely the first obligate carnivores requiring coordinated hunting strategies. The complexity of neural networks not just brain size
The implication is profound: what we experience as consciousness – including the sense of a planning, contemplating self separate from mere bodily function – may be largely an epiphenomenon of motor planning circuits. The “self” that thinks itself a contemplative being arose from neural architecture built primarily for movement through space. Consciousness arrived as a late narrator to systems designed for motor execution.
The Body as Proof of Impermanence
The Buddhist teaching that attachment to impermanent phenomena causes suffering finds its most literal expression in human physiology. The body itself demonstrates that clinging to stability generates the very suffering we seek to avoid. Consider the pathology of immobility: within days of physical stasis, measurable sarcopenia begins, insulin resistance escalates, bone resorption outpaces formation, and inflammatory markers rise. The body has no “maintenance mode” – only adaptive flux toward either development or degradation based on demand signals.
This isn’t metaphorical. Unused muscle atrophies, immobile joints develop strictures, unstressed bones demineralize, and even caloric substrates that aren’t metabolized through movement become pathogenic, accumulating as inflammatory adipose tissue that actively secretes cytokines. The body interprets stillness as a signal to conserve resources and shut down systems. Physical stasis is genuinely pathogenic.
The person who clings to comfort or the illusion of bodily stability – who remains sedentary, avoiding effort – creates the very disease they fear. There is no static “healthy body” to possess or preserve, only dynamic processes that must be continually engaged through movement. The self that refuses movement clings to an illusion, and physiological consequences follow as predictably as any natural law.
Movement and the Evolution of Self
This imperative for movement isn’t incidental to human nature – it built our species. The emergence of Homo erectus approximately 1.9 million years ago marked the first major brain expansion in our lineage, with cranial capacity jumping from ~600cc in Homo habilis to ~900cc. Much of this expansion occurred in motor cortex, prefrontal regions, and areas integrating planning with execution.
Bipedalism, which had emerged millions of years earlier in australopithecines, freed the hands and elevated the head, expanding visual range and foraging efficiency across savanna landscapes. But the feedback loop between upright posture, expanded foraging range, tool use, and brain development created an unprecedented selection pressure for sophisticated motor-cognitive integration. H. erectus were the first hominins to leave Africa, to create Acheulean hand axes requiring complex sequential motor patterns, and likely the first obligate carnivores requiring coordinated hunting strategies.
The implication is profound: what we experience as consciousness – including the sense of a planning, contemplating self separate from mere bodily function – may be largely an epiphenomenon of motor planning circuits. The “self” that thinks itself a contemplative being arose from neural architecture built primarily for movement through space. Consciousness arrived as a late narrator to systems designed for motor execution.
The Flowing Substrate
Yet even as these functions persist, the physical components that generate them are in constant flux. The human body exchanges most of its molecular constituents multiple times while preserving function. Intestinal epithelium turns over every 3-5 days. Red blood cells cycle every 120 days. Skin cells renew every 2-4 weeks. Even supposedly permanent structures prove dynamic: bone completely remodels every decade through coupled osteoclast-osteoblast activity. Neurons, while not typically replaced in most brain regions, continuously regenerate synapses, dendrites, and protein constituents with half-lives measured in days to weeks.
The Ship of Theseus becomes literal physiology. Within 7-10 years, nearly every atom in your body has been exchanged with the environment. Yet memory persists, personality remains recognizable, and learned motor patterns endure. The pattern maintains fidelity while the substrate flows through it.
What makes this particularly challenging to concepts of self is that consciousness itself – that most intimate sense of “I am” – emerges from this flux. The neural correlates of self-awareness depend on electrochemical gradients maintained by ion pumps consuming 20% of your resting metabolic energy, neurotransmitters synthesized and degraded within milliseconds, membrane receptors trafficking in and out of synapses hourly. The feeling of continuous selfhood is assembled moment-to-moment from components that never remain the same.
The self, then, is a functional pattern rather than a thing. It’s a verb masquerading as a noun – a process of continuous reconstruction that creates the illusion of stability only through its own persistence in regenerating itself. The very mechanism that maintains “you” simultaneously proves there is no permanent “you” to maintain.
The Thermodynamic Imperative
This energy-intensive maintenance of membrane integrity and cellular function obeys thermodynamic law. The second law of thermodynamics demands that global entropy increases inexorably. Living systems represent pockets of local order that temporarily decrease their own entropy only by exporting disorder to their surroundings. This requires constant energy input.
The ion pumps maintaining your membrane potentials – the electrochemical gradients enabling neural firing and the emergence of consciousness – are actively fighting against thermodynamic equilibrium. Left without energy input, concentration gradients dissipate, membranes depolarize, and the intricate electrochemical architecture collapses toward maximum entropy within minutes.
The approximately 10^20 ATP molecules you hydrolyze daily aren’t maintaining a structure – they’re maintaining a departure from equilibrium. The “self” that experiences continuity is actually a dissipative structure, analogous to a whirlpool or flame: a persistent pattern that exists only through continuous throughput of energy and matter. Interrupt the flow, and the pattern vanishes instantly.
This reveals the self’s deepest ontological status: it cannot be a thing-in-itself because it exists only as a temporary resistance to thermodynamic dissolution. You’re not a noun being maintained but a verb being performed – an active process of entropy export that momentarily concentrates order at the cost of increasing disorder elsewhere. Every thought, every moment of self-awareness, every experience of “I am” represents a local victory over entropy that simultaneously accelerates the universe’s march toward heat death.
Implications for Practice
Buddhism intuited what physics later formalized: clinging to a permanent self is like trying to grasp a flame. The flame exists, produces light and heat, can even be passed between candles – but it’s never the same combustion reaction from moment to moment. Similarly, the “you” experiencing this insight is already thermodynamically distinct from the “you” who began reading this sentence.
This isn’t nihilism. Function persists even as substrate changes. Consciousness continues even as its physical basis regenerates. But the persistence is active, not passive – a constant reconstruction rather than the preservation of something already complete. Understanding anattā doesn’t dissolve experience but reveals its true nature: not a possession to be guarded but a process to be engaged, not a static self to preserve but a dynamic pattern that exists only in its continuous becoming.
The body, in its requirement for movement, its molecular turnover, and its thermodynamic precarity, becomes the perfect teacher of non-self. Every breath, every heartbeat, every neural firing demonstrates that what we call “I” is really a temporary deviation from equilibrium, maintained only through ceaseless exchange with what we mistakenly call “not-I.” The boundary was always illusory. What remains is the process itself, and the recognition that this process never needed a permanent owner to unfold.