What Makes a Living Being the Same Being?

Identity as Continuity of Causal Organization Through Transformation

A living being changes throughout its existence. Its molecules are replaced. Many of its cells turn over. Its boundaries are repaired. Its metabolism changes with activity, sleep, illness, development, and ageing. Its internal organization is repeatedly modified by growth, experience, injury, repair, and environmental change. Yet we ordinarily say that the infant, the adult, the injured patient, and the recovered patient can be the same living individual. This raises a harder question than asking what life is:

What makes a changing living being remain the same being?

The answer cannot simply be:

• the same matter;
• the same shape;
• the same genome;
• uninterrupted visible activity;
• or sufficient similarity.

Two organisms can be almost indistinguishable and still be two individuals. One organism can change radically and remain one continuing individual. Connection Theory proposes a more specific answer:

A living being remains the same biological individual when its later causal organization arises through the continuing physical causal lineage of its earlier causal organization under a specified individuation frame.

What persists is therefore not a frozen set of components. Nor is it a perfectly unchanged network of causal relations. It is:

continuity of causal organization through transformation.

1. The Same Organism Is Not the Same Matter

Living organisms exchange matter continuously. They take in:

• oxygen;
• water;
• nutrients;
• ions;
• carbon;
• microbial material.

They release:

• carbon dioxide;
• heat;
• waste;
• water;
• shed cells;
• metabolites.

Human cell turnover varies sharply across tissues; radiocarbon studies have demonstrated ongoing adipocyte turnover and much slower cardiomyocyte renewal in adults (Spalding et al., 2008; Bergmann et al., 2009). If biological identity required retention of exactly the same matter, an organism would cease to be itself almost immediately. But material continuity is not sufficient either. A dead body can retain much of the same matter. A damaged structure can be rebuilt using original materials. A second organism could, in principle, be assembled from materially indistinguishable components. So:

Matter can change while identity continues, and matter can remain while identity is lost.

The relevant continuity must lie elsewhere.

2. Similarity Is Not Identity

Imagine two organisms that are molecularly indistinguishable at a particular moment. They have:

• the same genome;
• the same structure;
• the same measured internal state;
• and, if the thought experiment requires it, the same memories.

They still occupy two places. They can undergo two different futures. One can be injured while the other remains unharmed. One can encounter a new environment while the other does not. They are therefore two individuals, not one individual appearing twice. This reveals a basic distinction.

Qualitative identity

How similar are the two systems?

Numerical identity

Are they one and the same individual? Similarity can approach perfection. Numerical identity cannot be reduced to ever smaller state difference. Identical twins are not one person. Two clonal cells are not one cell. Two identical copies of a genome are not one physical molecule. Therefore:

Similarity is neither necessary nor sufficient for biological identity through time.

A later organism can be very different from its earlier state and still belong to the same continuing life.

3. Organization Does Not Mean an Unchanging Structure

A possible mistake remains. If identity is not matter, perhaps it is a fixed organization. But living organization is not fixed either. Development changes:

• cell populations;
• tissue relations;
• signalling structures;
• regulatory relations;
• boundaries;
• metabolism.

Learning and experience can alter neural organization. Injury and repair can alter anatomy. Ageing changes many causal relations. So identity cannot require:

the same causal relations at every moment.

That would make development itself an identity-breaking process. The stronger idea is:

Later causal organization must arise through the continuing causal lineage of earlier causal organization, whether through active transformation or preserved organization across an interruption.

The relations may change. What matters is how they change. A compact representation is: O(t₀) → continuing causal transformation → O(t₁) → continuing causal transformation → O(t₂) where each later organization is physically generated through the operation, modification, preservation, repair, or reorganization of the earlier one. The continuity lies in the causal lineage connecting the states, not in structural immobility or uninterrupted activity.

4. Identity Requires an Individuation Frame

Before asking whether something remains the same, we must specify what kind of thing is being tracked. A human organism contains:

• cells;
• tissues;
• organs;
• microbial populations;
• immune lineages;
• dynamically maintained compartments.

The organism can remain the same while one blood cell is replaced. A tissue can remain the same while many constituent cells turn over. A species can persist while every organism in one generation is replaced by descendants. These are different identity questions. Connection Theory calls the prior choice of tracked unit an individuation frame. The frame specifies:

• the organizational scale;
• the relevant boundary relations;
• the type of individual being tracked;
• the continuity relation of interest;
• which events count as continuation, replacement, reproduction, branching, fusion, or loss.

This does not make identity arbitrary. The observer chooses whether to track a cell, organism, colony, or lineage. But once that frame is specified, whether later states were physically generated through earlier states is an empirical question.

The unit of identity is selected. The history of that unit is not invented by the observer.

This essay concerns diachronic biological identity of organisms. It does not attempt to settle psychological personhood, legal identity, consciousness, or continuity of subjective experience.

5. Replacement at One Level Can Preserve Identity at Another

Allogeneic haematopoietic stem-cell transplantation provides a useful example. After successful transplantation, substantial portions of the recipient's blood-forming system may become donor-derived, a transition that can be quantified through donor-chimerism measurements (Nucera et al., 2024). The patient does not thereby become the donor. Nor is the patient ordinarily treated as a newly created organism. At the level of the whole organism, donor-derived cells enter an already continuing:

• circulation;
• marrow environment;
• immune interaction network;
• nervous system;
• anatomy;
• metabolic organization;
• historical trajectory.

The material source of an important subsystem changes while the organism continues. This reveals a general principle:

The origin of replacement material does not, by itself, determine the identity of the larger organization into which that material becomes integrated.

What matters is how the replacement occurs. The donor cells are incorporated through the recipient's continuing causal organization. They do not independently construct a second organism and then substitute for the first. The same logic applies to:

• organ transplantation;
• prostheses;
• artificial valves;
• ordinary tissue repair;
• many forms of component turnover.

Component replacement can preserve higher-level identity when the replacement occurs through the continuing causal organization of the higher-level individual.

6. Continuous Visible Activity Is Not Necessary

Continuity should also not be confused with uninterrupted visible activity. A mature seed can remain dormant and later resume coordinated metabolism and development. Tardigrades can tolerate near-complete dehydration by entering a reversible, metabolically inactive anhydrobiotic state (Tanaka et al., 2015). The empirical details of whether activity reaches literal zero are not decisive for the identity problem. What matters is that the organism's own material organization enters a state from which later living dynamics can emerge through that preserved organization. This requires several distinctions: Active realization
Living dynamics are visibly operating. Strongly suppressed activity
Many processes are greatly reduced. Preserved causal organization
The material organization needed for later continuation remains present.

Reactivation through that organization
Later activity develops from the preserved earlier system. Therefore:

Visible activity can disappear while organismal continuity remains.

What matters is not uninterrupted performance. It is whether the later living organization arises through the continuing physical history of the earlier one.

7. Suspension Is Not Reconstruction

Consider two cases.

Case A — Suspension

An organism enters a low-activity state. Its internal organization changes into a protective configuration. The same materially embodied system remains present. When suitable conditions return, preserved structures participate causally in renewed activity.

Case B — Reconstruction

The original organism is destroyed. A detailed record of its state remains. Later, an external process uses that description to assemble another system with the same measured organization. The second system may be extraordinarily similar. It may reproduce:

• the same genome;
• the same structure;
• the same memories;
• the same represented history.

But the causal route is different. In suspension:

later organization develops through preserved earlier organization.

In reconstruction:

later organization is generated by an independent construction process using information about the earlier system.

This is why:

A description of an individual is not the individual whose state it describes.

Information can preserve similarity. It does not by itself preserve causal-organizational continuity. But informational form is not automatically disqualifying either. A frozen or serialized state can participate in continuity when it is itself the causally descended state carrier of the tracked system and later resumption follows that provenance path. What fails here is independent reconstruction from an external description after the earlier lineage has ended, not information-mediated preservation as such.

8. Historical Content Is Not Historical Connection

Two ideas about history must also be separated.

Historical content

What traces, memories, records, or structural consequences of the past are represented in the current system?

Historical connection

Did this current system actually arise through the continuing physical transformation of the earlier system? A copy can reproduce historical content. It cannot retroactively acquire the physical history through which the original became what it was. This difference does not require any nonphysical essence. It is entirely physical. Two perfect copies can:

• occupy different locations;
• arise from different construction events;
• belong to different causal histories;
• continue into different futures.

So:

History is not an extra substance inside the state. It is the physical relation connecting states across time.

A snapshot can describe what a system is like now. It cannot, by itself, establish which earlier system this one physically continued from.

9. Causal-Organizational Continuity

We can now state the central proposal more precisely. A later state belongs to the same biological individual when, under a specified individuation frame, the later causal organization is generated through a traceable continuation of the earlier causal organization. Several conditions matter.

1. Causal succession

Later states are physically generated through earlier states by a traceable sequence of transitions. The earlier organization makes a specific causal contribution to the later one.

2. Organizational transformation

The causal organization can change through:

• growth;
• development;
• repair;
• replacement;
• reorganization;
• dormancy;
• physiological transformation.

Continuity does not require static relations. It requires that later organization be generated through earlier organization.

3. Continuation through the existing organization

External support can participate. But it acts through a still-continuing organism rather than independently creating a replacement after that organism's organizational continuity has ended.

4. Frame-consistent traceability

The same individuation frame must be applied across the interval. Scale and continuity criteria cannot be changed after the outcome merely to preserve a preferred identity judgment.

5. Branch-sensitive treatment

One earlier organization can sometimes generate several successor organizations. Causal inheritance can branch even when exclusive numerical identity no longer provides one unique answer. Together, these conditions define:

causal-organizational continuity through transformation.

10. External Assistance Does Not Automatically Break Continuity

Living systems are never causally isolated. They depend on environments. Medical support can become substantial. A patient may depend on:

• ventilation;
• dialysis;
• medication;
• surgery;
• implanted devices;
• transplanted organs.

External causal contribution does not automatically create a new organism. The important question is not:

Was an external cause involved?

It is:

Did the later state arise through the continuing causal organization of the tracked organism, or was a new organization independently constructed after that continuity had ended?

A ventilator can support an existing organism. Surgery can reconnect tissues. A transplanted organ can become integrated into a continuing body. The presence of external assistance is therefore compatible with identity continuity.

11. There Is No Universal Percentage of Permitted Change

The same is true of replacement speed. There is no obvious universal absolute turnover rate above which identity must fail. What matters is whether the organism's regulatory and reconstruction processes preserve the relevant organization as components turn over. In schematic terms, the important comparison is between a replacement timescale and a reconstruction/regulation timescale: can the organization restore roles, relations, boundaries, and viable state at least as fast as turnover disrupts them?

This makes persistence a dynamical relation rather than a percentage rule. Rapid molecular or cellular turnover can be compatible with the same organism when the higher-order organization remains continuously maintained.

How much of an organism can be replaced before it becomes a different individual? There is unlikely to be one universal percentage. Replacing a small but organizationally critical structure can destroy continuity. Replacing a much larger amount of rapidly renewing material may preserve it. The significance of a change depends on:

• what changed;
• how it changed;
• how replacement was sequenced;
• whether the relevant organizational relations remained continuous;
• whether later organization was generated through the earlier system;
• whether the lineage remained single or branched.

This is why:

The amount of change matters less than the causal organization of the change.

12. The Vortex Intuition

A vortex can preserve a recognizable pattern while the water constituting it continuously changes. If we slow the vortex dramatically, it may look almost like a static object. If we accelerate the processes of a living organism dramatically, the organism may look more like a turbulent flow. The difference partly reflects observation timescale. This illustrates why visual stillness is a poor criterion for identity.

A vortex can change position and shape through continuous flow while remaining one tracked dynamical pattern under an appropriate frame. If it disappears and another vortex is later generated elsewhere from recorded measurements, the later vortex can resemble the earlier one without sharing its continuous flow history. The analogy is limited. A vortex is not automatically alive. But it clarifies one point:

Identity through time depends on continuity of process, not visual immobility.

Living organisms add more demanding conditions because their continuity includes living boundaries, repair, preserved organization, and ongoing causal transformation.

13. Division and Fission Reveal the Limit of Exclusive Identity

Some biological processes do not produce one later individual from one earlier individual. They produce several successors. Planarian fission provides a useful example. In asexual Schmidtea mediterranea, transverse fission produces fragments that regenerate missing structures and continue as separate animals (Arnold et al., 2021). Both successors inherit:

• matter;
• organization;
• causal history;
• living capacity

from the pre-fission organism. Neither is an independently manufactured copy. The physical causal-organizational inheritance is real. But a problem appears if we insist that both later organisms are numerically identical to the one earlier individual. The two successors are not identical to each other. So exclusive identity cannot simply branch without qualification. Connection Theory therefore separates:

Causal-organizational inheritance

Which later organizations were physically generated through the earlier organization? This can branch.

Exclusive numerical identity

Which later system, if any, should be counted as the one unique continuation of the earlier individual? This depends on the individuation rule and may cease to have one unique answer at a symmetrical branching event. Thus:

Causal continuity can branch. Exclusive numerical identity need not.

Fission is therefore not the same thing as death. Living causal organization can continue through several descendants even when one exclusive identity label no longer applies cleanly.

14. Copying as an Intuition Test

Imagine a machine that produces an exact biological copy while leaving the original intact. Immediately afterward there are two organisms. Each may possess:

• the same memories;
• the same structure;
• the same preferences;
• the same represented historical content.

But they occupy different locations and begin different physical futures. The copy did not become the original. Now suppose the original is destroyed immediately before the copy is activated. Does destruction of the original make the copy numerically identical to it? The copy's construction process has not changed. Its physical history has not become the original's earlier history. Only the presence of a competing survivor has changed. This protects an important principle:

Identity should be evaluated from the causal structure of the transition, not from whether another competing copy still exists.

Destroying the original later cannot retroactively convert independent reconstruction into continuity. This principle should not be confused with branch-sensitive continuity over a pre-declared adjudication interval. If one causally descended dormant state later generates multiple independently continuable successors within that declared interval, the lineage itself has branched. That is a change in the causal lineage being evaluated, not a retroactive upgrade of an independently reconstructed copy.

This argument does not prove that all replacement interrupts identity. Gradual replacement may occur through one continuously transforming organization. The relevant distinction is again:

continuation through transformation versus independent reconstruction.

15. Organization Comes Before Organizational Continuity; Identity Comes After

The updated Connection Theory vocabulary makes the logical order clearer.

Organization

The system consists of regularized causal relations that form an empirically distinguishable organized inside and outside.

Organizational Persistence

During ongoing life, the organism persists through material flow and node turnover because relevant boundaries, roles, relations, and regulatory processes remain continuously reconstructible. This is Organizational Persistence.

Organizational Continuity

Across interruption or resumption, the stricter question is whether later causal organization is generated through the continuing lineage of earlier causal organization.

Identity

Under a specified individuation frame, different temporal states are attributed to the same biological individual because they belong to that continuing causal-organizational history. So the direction is: Causal Organization → Organizational Persistence through turnover → Organizational Continuity across interruption where relevant → Identity Attribution. Identity does not create continuity. The underlying physical history constrains the identity judgment.

16. A Working Definition of Diachronic Biological Identity

Connection Theory proposes the following working definition:

A later living system is the same biological individual as an earlier living system when, under a specified individuation frame, its later causal organization is generated through the continuous physical transformation, repair, reorganization, or preservation of the earlier causal organization rather than through an independent reconstruction process; where that causal-organizational history branches into multiple independently continuing successors, causal inheritance may continue along several branches even when exclusive numerical identity no longer has one unique continuation.

Several clauses matter.

A later living system

The question concerns persistence across time.

A specified individuation frame

Cells, organisms, colonies, symbiotic systems, and species can require different identity criteria.

Later causal organization generated through earlier causal organization

This is the core continuity condition.

Transformation rather than immobility

Development, repair, replacement, and reorganization are compatible with continuity.

Not independent reconstruction

State similarity and copied historical content do not establish continuity by themselves.

Branch sensitivity

Biological continuation can generate several descendants. The physical inheritance can be real even when exclusive identity becomes non-unique.

17. The Central Claim

A living individual is not:

• a fixed collection of matter;
• a frozen structure;
• a static information file;
• or whichever later system looks most similar.

It is a historically extended causal organization whose later states arise through the continuing physical transformation of its earlier organization. So:

The same matter is not necessary.
The same structure is not necessary.
The same information is not sufficient.
Continuous visible activity is not necessary.
Continuity of causal organization through a continuing physical lineage is the central requirement.

A dormant organism can remain the same organism when its own causal organization is preserved in a form from which later living dynamics arise. A repaired organism can remain the same organism when repair occurs through its continuing organization. A copy can reproduce structure and historical content without inheriting the original physical history. A branching lineage can generate several living descendants without requiring one exclusive identity label to apply to all of them. The simplest expression is:

A living being remains itself not by resisting change or by remaining continuously active, but because its later causal organization arises through the continuing physical causal lineage of its own earlier causal organization.

18. The Next Question

If biological identity depends on continuity of causal organization through transformation, when does that continuity end? The answer cannot simply be:

• when all activity stops;
• when one function disappears;
• when the system looks damaged;
• or when some components can no longer recover.

The final essay asks a more precise question:

When has the continuing causal organization of the living individual been lost in a way that no longer permits the same organism to continue as a living system?

Part IV — What Is Death?

References

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• Nucera, S., Sindoni, M. M., Bugarin, C., et al. (2024). A novel flow-cytometric based method to assess post-HSCT donor chimerism exploiting RNA hybridization. Bone Marrow Transplantation, 59, 171–177. DOI: 10.1038/s41409-023-02143-9.
• Spalding, K. L., Arner, E., Westermark, P. O., et al. (2008). Dynamics of fat cell turnover in humans. Nature, 453, 783–787. DOI: 10.1038/nature06902.
• Tanaka, S., Tanaka, J., Miwa, Y., et al. (2015). Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLOS ONE, 10(2), e0118272. DOI: 10.1371/journal.pone.0118272.