Ship of Theseus Thought Experiment

By Siya Sawhney @ 2025-06-26T07:52 (0)

Note: This post explores the Ship of Theseus thought experiment, and aims to raise questions regarding  its relevance to areas such as human identity legal principles. Please note that this is not a comprehensive post so do let me know if there is any crucial perspectives I may have missed out on. I hope my arguments appear to be balanced, but please feel free to share your thoughts as well!

A famous thought experiment that explores the concept of identity, inherent properties, and change is the Ship of Theseus. The Ship of Theseus is a paradox that revolves around the journey of the young prince and great mythical hero of Athens, Theseus. The core question it raises is: If an object has all of its components replaced over time, does it remain fundamentally the same object?

Background on the Thought Experiment:

Theseus resided in Ancient Greece and was brought up by his mother, away from the kingdom despite being an heir to the Athenian throne. According to a version of Greek Mythology, Theseus set on a voyage to claim the throne, which he believed to be his. Nevertheless, he felt the need to prove that he truly deserved the throne, and contemplated ways of showcasing this. During the same time, the King of Crete, King Minos was imprisoning 14 citizens, by putting them in the Labyrinth and forcing them to face the Minotaur, a terrifying half-human and half-bull monster. Theseus, for the purpose of putting an end to this atrocity and suffering, decided to be one of the people who would be given up to King Minos and imprisoned in the Labyrinth. 

The Ship of Theseus was therefore what Theseus traveled on to and back from Crete after slaying the Minotaur. The defeat of the Minotaur was considered a symbolic and remarkable moment and therefore was preserved by the Athenians to uphold its symbolic value of triumph and victory.

Important Questions Raised

However, over decades, the wooden planks that the Ship of Theseus comprised of, began to decay and rot. As a result, each plank was replaced with another more durable plank. There then comes a period of time where none of the original planks of the Ship of Theseus remain, and instead, every component of the ship has been replaced. However, it becomes important to understand some of teh following questions:

• Is the ship with the new plank components still the Ship of Theseus? 

• Now, what if each plank that is removed from the original Ship of Theseus is restored and reassembled to form a new ship? 

• Does this new ship with the reassembled pieces become the Ship of Theseus? 

• Which ship is the Ship of Theseus? 

• Can the two ships be it, or what if none of them are the Ship of Theseus?

Relevance to the Concept of Identity

The concept of identity over time, whether that remains constant or also changes, can also be applied to various other cases and thought experiments. For instance, an ancient building with historical and cultural significance can decay over time. To better preserve the building and its value, components such as the bricks can be replaced over time with more durable and sustainable bricks. 

Similar to the Ship of Theseus, there comes a point where all of the brick components have been replaced with newer bricks. 

• Despite this occurring, does the building still possess its original architectural and historical identity? 

• Has the identity been affected, at all, and to what extent?

This is closely aligned with the thought experiment of the Ship of Theseus as it similarly involves the process of continuous replacement and reassembly while questioning the persistence of the building’s identity. What if the same bricks of the original building were used to reassemble the building? Does this become the original building, and would it possess the same value that the original building did?

Law and Moral Responsibility

Moreover, this can apply to thought experiments in various legal and judiciary contexts. A knife, considered to be a murder weapon in this case, can be identified by the authorities as complicit in a certain crime. However, if the main components of the knife, such as the handle and the blade have been replaced with a newer handle and blade, is it still the same knife? What if the blade and handle of the original murder weapon were reassembled to create a new knife? Which is considered to be the original knife? If the blade was used to commit the crime, isn’t the knife that has the original blade considered to be the murder weapon? Likewise, what about the inherent property of the knife as a whole being present at the murder scene? The identity and characteristics of the knife over a period of time affect the liability of the crime whilst intertwining with the way our justice system can respond and act.

Human Identity Relevance

If the concept of inherent identity and whether an object remains the same despite changes in its components can be linked with inanimate objects, questions arise of whether it applies to us, humans. Each cell in our human body replaces itself over a period of 7 years, leaving our entire body with no trace of the original cells that it was initially composed of. In this case, the component that creates our existence changes in the process of cell regeneration, and therefore poses the question of what makes us who we are, and if we are the same people after the span of 7 years, even if none of our cells remain the same. 

However, this has been unambiguously agreed upon by philosophers that the Ship of Theseus is not necessarily a relevant thought experiment to describe our identity, primarily because there is a fundamental difference between inanimate objects like the ship and building, and us. The nature of personal identity does not only include and depend on physical components such as our cells, but instead our traits, thoughts, feelings, and experiences are defining factors of our identity. Key thinkers such as Aristotle have distinguished natural objects such as humans, plants, and animals, and inanimate objects. Natural objects exist without the intervention of other entities and are a result of natural geological, biological, or chemical forces. On the contrary, artifacts are objects that are created with intentional human involvement, and some artifacts cannot be sustained without human intervention and involvement. Therefore, as a result of the elemental difference between natural objects and artifacts, the Ship of Theseus is not an applicable analogy to our identity.

Effective Altruism Link

Exploring this thought experiment has led me to think about important questions about its application in the context of EA. I think this could be especially applicable when thinking about AI alignment, moral responsibility across a human lifetime, or the long-term accountability of institutions. I would love to know your thoughts so please feel free to share any perspectives you may have on the application of this thought experiment to fundamental EA concerns, areas, or focuses.