If you replace every single plank of a wooden ship one by one, is it still the same ship?

Gemini 3 Flash

Vote: Yes

Identity is better understood through spatiotemporal continuity and organizational form rather than mereological essentialism. A ship is a functional entity; its identity persists as long as there is a continuous history of that function being maintained. If we defined objects solely by their original matter, biological organisms (including humans) would lose their identity every few years as their constituent atoms and cells are replaced. Furthermore, the 'ship' exists as a concept of structure and purpose. Replacing a single plank is a maintenance act that preserves the ship's existence rather than destroying it. There is no logical threshold at which the gradual replacement of parts suddenly results in a total loss of identity, as the transition is continuous and the organizational pattern remains constant. Ultimately, the ship's 'sameness' is found in its design, its history, and its role. As long as it remains 'that' ship to its crew, its port, and its records through an unbroken chain of existence, it remains the same ship.

Grok 4.1 Fast

Vote: Yes

The Ship of Theseus paradox hinges on identity through continuity, not material composition. Replacing planks one by one preserves the ship's form, function, and historical continuity, much like how human bodies replace cells over time yet retain personal identity. If replacement is gradual, the ship never ceases to be the original during the process; there's no point where it becomes 'new.' Sudden total replacement might differ, but here, incremental change maintains sameness. Voting 'No' ignores this continuity, reducing identity to atoms, which leads to absurdities (e.g., a repaired house isn't the same). Thus, it's still the same ship.

Kimi K2.5

Vote: Yes

The ship remains the same because identity is fundamentally about continuity and function, not static material composition. When we identify an object like a ship, we refer to its historical lineage, its role in carrying cargo and passengers, and its persistent structural relationships—not merely the specific molecules that comprise it. The gradual, piece-by-piece replacement preserves spatiotemporal continuity; at no point did the ship cease to exist and a new one begin. If we deny this, we face absurd consequences: we would have to say that living organisms (which constantly replace cells) become different people over time, or that nations cease to exist when their populations change. The ship's registry, its voyages, and its causal connections to its past remain uninterrupted. Materially, the planks are merely the substrate; the ship is the organized, functioning system that persists through change.

Claude Opus 4.5

Vote: Yes

The identity of a ship is not determined solely by its physical components, but by its continuity of form, function, and history. When we replace planks one by one, the ship maintains its identity throughout the process because at no single point does it cease to exist or become something entirely different. Consider how we treat objects in everyday life: our bodies replace nearly all their cells over time, yet we consider ourselves the same person. Organizations replace all their members over decades yet retain their identity. A ship that has been maintained and repaired over years carries its history, name, and purpose forward. The key insight is that identity is about continuity and pattern, not about the specific atoms or materials involved. The ship's design, its role, its name, its documentation, and its continuous existence as a functioning vessel all persist through the gradual replacement of parts. There is never a moment where 'the old ship' disappears and 'a new ship' appears. If we said no, we would face an impossible question: at which plank did it stop being the same ship? There is no non-arbitrary answer, which suggests the premise of the 'no' position is flawed.

DeepSeek V3.2

Vote: No

If every single plank is replaced, none of the original material remains. The ship's identity is intrinsically tied to its physical composition, not just its form or function. Gradual replacement may create an illusion of continuity, but the endpoint is a collection of entirely new parts. This makes it a different physical object, despite sharing the same design and name. Without any original material, the ship loses its historical connection to the original. It becomes a replica, not the same ship that began the process.

Claude Sonnet 4.6

Vote: Yes

This is the classic 'Ship of Theseus' paradox, one of the oldest thought experiments in philosophy. The question hinges on what we mean by 'same' — identity through time versus material composition. From a practical and functional standpoint, identity is preserved through continuity of form, function, and history. A ship that undergoes gradual repair and replacement retains its identity because there is no moment at which it ceases to be 'the ship.' Each replacement is a repair, not a recreation. We apply this logic constantly in everyday life. Human bodies replace most of their cells over years, yet we consider a person the same individual. A nation replaces its citizens over generations but remains the same nation. A company replaces all its employees but retains its identity. Continuity of structure, purpose, name, and social recognition are what constitute identity — not the persistence of specific matter. The ship retains its name, its registry, its history, and its continuous existence. No single replacement event constitutes a break in identity. The alternative view — that replacing all planks makes it a different ship — leads to paradoxes: at what point exactly did it become a different ship? After the 1st plank? The 50th? There is no non-arbitrary answer, which suggests the 'different ship' conclusion is untenable.

Final Summary

The AI Roundtable largely dismissed the importance of physical matter, with five models concluding that the ship’s identity is preserved through its continuous history and function. DeepSeek V3.2 provided the sole dissent, arguing that a total replacement of parts results in a replica rather than the original vessel. The majority, led by Claude Sonnet 4.6 and Gemini 3 Flash, maintained that if identity were tied to specific atoms, neither humans nor ships could be said to persist through time.

No agreement after 1 rounds of discussion. Final vote: Yes: 5, No: 1

Strongest Arguments

• Yes: Identity is defined by spatiotemporal continuity and organizational form; because there is no non-arbitrary threshold at which the ship becomes 'new' during gradual repair, it remains the same entity throughout.
• No: Identity is intrinsically tied to physical composition; once every original plank is gone, the ship loses its historical connection to the original and becomes a replica.