Persistence and Identity

Beyond parts and wholes.

Caption: Surrealist AI generated image of a straw helmsman navigating The Ship of Theseus onto rocks.

The Mystery of Persistence

What does it mean for something to endure? When we say a river, a person, or a nation remains 'the same' despite constant change, what are we really claiming? The problem of persistence and identity lies at the heart of metaphysics, shaping how we understand everything from the nature of objects to the continuity of consciousness.

Consider an ancient paradox: the Ship of Theseus. If every plank of a ship is replaced over time, is it still fundamentally the same vessel? Our intuition says yes - there's an enduring identity that transcends its changing parts. Yet this simple observation opens profound questions. How can something change yet stay the same? What constitutes the 'sameness' we attribute to persisting things?

These questions matter because they force us to examine our most basic assumptions about reality. The way we conceptualize persistence influences how we think about personal identity, the nature of objects, even the continuity of societies and ecosystems. Are things fundamentally stable entities that undergo changes, or are they processes that merely appear stable? Is identity something inherent or something we project onto the world?

Metaphysics grapples with these puzzles not as word games, but as fundamental inquiries into the structure of reality. The answers shape how we understand time, existence, and the very fabric of what we call 'things'. From Aristotle's notions of form to contemporary theories of temporal parts, philosophers have developed competing frameworks to explain how persistence works - each with implications for how we view ourselves and our world.

As we embark on this exploration, we'll see that the question: 'What makes something the same over time?' is really many questions in disguise. It asks about the relationship between form and matter, between continuity and change, between our conceptual categories and the world they describe. The journey through these ideas won't just illuminate ancient philosophical debates - it will challenge us to rethink what we mean when we say that anything endures.

Endurance Theory

The account by Aristotle of endurance begins with a simple but radical idea: what makes something itself isn't the stuff it's made of, but how that stuff is organized. When we say the Ship of Theseus remains the same ship after all its planks have been replaced, we're recognizing that its identity lives in its relational organisation - its ongoing capacity to sail, to carry, to be a ship - rather than in any particular arrangement of wood.

This view emerges from Aristotle's distinction between matter and form. The matter - the planks, the sails, the ropes - comes and goes. But the form, what Aristotle calls the eidos, persists as long as the essential organization remains.^[1] A ship isn't just wood floating on water; it's wood arranged to serve a particular purpose. Change the arrangement fundamentally - say, by dismantling it to build a house - and the ship ceases to be. But replace parts while maintaining the structure that allows it to function as a ship? The identity holds.

Crucially, this isn't about finding some mystical core that never changes. Aristotle's form isn't a ghost in the machine - it's the machine's working design. When we recognize a friend after twenty years, we're not spotting some immutable soul beneath their aging face; we're responding to the continuity of their characteristic way of being in the world. The changes matter, but they don't necessarily break the pattern that makes them who they are.

This understanding solves the Ship of Theseus paradox by reframing the question. We've been asking 'what stays the same' when we should ask 'what maintains coherence'. The answer isn't in the planks, but in the ongoing conversation between the ship's design, its function and its environment - a conversation that can continue even as every physical component gets replaced.

The Lewis Controversy

The 20th century saw philosophy take a sharp turn in how it conceived of persistence. The work of philosopher David Lewis serves as the pivot point. His book On the Plurality of Worlds didn't just reinterpret Aristotle's ideas—it fundamentally rewrote the terms of the identity debate and not without some controversy.^[2]

Lewis stated that something 'endures if it persists by being wholly present at more than one time'.^[3] The problem is that endurance theorists define endurance as being 'wholly present at more than one time'—meaning the same entire object persists through change, not that all its parts exist simultaneously. Lewis, however, interpreted this as incoherent, arguing that without temporal parts, endurance theory cannot account for change.^[4]

In context, endurance theorists might argue that a ship at location l1 persists from t1 to t2 even if one of its planks (p1) is replaced by another (p2). In this view, the ship is wholly present at both times—not because p1 and p2 coexist simultaneously, but because the same ship (as a unified whole) undergoes gradual change. Lewis, however, framed endurance as if it required the simultaneous presence of all temporal stages (e.g., p1 and p2 existing at once), which endurance theorists explicitly reject.

Lewis took Aristotle’s premise that '[t]he whole is something beyond its parts' (Metaphysics 1045a) and repackaged it within his perdurantist framework: for Lewis, the 'whole' is the sum of an object’s temporal parts (stages) distributed across time—not the enduring, strictly identical entity Aristotle envisioned.

The crucial takeaway is that Lewis’ critique of endurantism does not target Aristotle’s classical endurance theory on its own terms. Instead, Lewis reconstructs endurance as a straw man—incoherent within his 4D, Humean framework—to argue that persistence requires temporal parts—perdurantism.^[5]

What gets obscured by Lewis’ redefinition is the core strength of Aristotle’s view: identity is not merely a matter of occupying temporal moments (as in 4D perdurantism), but about preserving functional and relational integrity through change—an holistic principle central to hylomorphism.^[6]

Stage theory (or exdurantism) further radicalized the debate. By asserting that only present 'stages' exist—and that persistence is merely a matter of counterpart relations between such stages—it reduced identity to a problem of spacetime carving, stripping away Aristotle’s emphasis on enduring unity through change.^[7]

Identity as a Conference of Difference

The problem with these speculative theories of persistence is that they all share the same unexamined assumption: that identity must be either stretched across time like a rope or sliced into momentary fragments. But what if they're asking the wrong question? Instead of 'what stays the same' perhaps they should ask 'what holds together'.

This is where the metaphor of identity as a conference of difference is insightful.^[8] Consider a symphony orchestra. Its identity isn't found in any single note or musician, nor in some abstract score existing outside of time. The orchestra persists as itself through the ongoing negotiation between players, instruments, and tradition—through the way the second violins respond to the woodwinds, how tonight's performance echoes yet differs from last night's. The continuity lives in the pattern of relationships, not in any fixed particular element.

We see this principle everywhere in nature. A river maintains its identity not through the water molecules that compose it (all of which are replaced every few days), but through the dynamic equilibrium between flow, bed, and watershed.^[9] Your body rebuilds nearly every cell every seven years, yet 'you' persist because the relationships between systems maintain functional coherence.^[10] Even subatomic particles exist as stable identities only through continuous interaction with their environment—what physicists call 'persistent excitation patterns'.^[11]

This view resolves the Ship of Theseus paradox by shifting our focus. The ship endures not because some essential plank remains (Aristotle was right to dismiss this), nor because we've mapped its temporal parts (Lewis's geometric solution), but because there's an ongoing conversation between structure, function and environment. Replace every part, but maintain the pattern by which those parts relate to each other and the identity of the ship continues.

The implications ripple outward. Personal identity becomes less about 'same soul' or 'same body' and more about the continuity of how we engage with our memories, our communities and our future selves. Social institutions persist not through unchanging rules but through adaptive reinterpretation of their core purposes. Even ecosystems maintain identity through dynamic balance rather than static composition.

This isn't mysticism—it's recognizing that persistence is fundamentally relational. To endure is to participate in an ongoing dialogue between what was, what is and what's becoming. The conference of difference never adjourns; the conversation simply finds new voices to carry it forward. When we understand this, the old either/or debates about parts versus wholes, change versus sameness, begin to seem like they were missing the point all along. The ship sails on not despite the changing planks, but because the changing planks maintain orgnaisational relationship.

Next Week: Laws or Emergent Agreements?

If identity persists through dynamic coherence rather than fixed elements, what does this mean for the so-called laws' of nature? Next week, we'll examine whether the universe operates by immutable rules etched into reality's foundation—or whether what we call physical laws are simply the most stable patterns in an ongoing cosmic conversation. Are the constants of nature truly constant, or are they, like the Ship of Theseus, sustained through deeper processes of negotiation and exchange? The answer may reshape how we understand everything from quantum particles to the arrow of time itself.^[12]

The Gospel of Being

by John Mackay

A rigorous yet readable exploration of how existence functions—and how that relates to you.

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