The paradox of Theseus’ ship is based on asking the question whether after all the parts that make up an object have been replaced, it can still be considered the same or would become a different object from the original one.

It is a paradox that has its origin in a legend from Greek mythology , which consists of various variations and questions in addition to the original. In this article we will review what this popular and mythical Greek paradox is about.

What is the paradox of Theseus’ ship?

The legend that gives rise to the paradox of Theseus’ ship tells that Theseus once returned from the island of Crete, along with his crew, and they were on a ship that was already quite old. During the journey (which was quite long) the ship became increasingly damaged. Every damage to the ship was repaired by the crew , with the broken piece being replaced by one in better condition, and sometimes the pieces were recycled and placed in different parts of the ship.

When Theseus and his crew arrived in port, the ship had been completely modified , there was not a single piece left from the ship in which they left the island of Crete, or else these had been recycled and placed in different places, as a new piece.

This particular event prompted a question from the philosophers of that time: “Is the ship in which Theseus and his crew came to port the same ship in which they left the island of Crete?

Explanation of the Paradox

The aim of this Greek paradox is to clarify in some way what is the essence of bodies and objects, their identity , which makes them unique.

Although the legend tells the story of Theseus’ ship and its crew, the paradox can be extrapolated to almost anything else. It is applicable to other situations and objects that experience an intense change in most of their initial parts .

Examples of the Paradox

Some good examples in our present time that can serve to adequately illustrate the paradox of Theseus’ ship are the following.

1. Repowering the computer

When people repower their computer, the process involves replacing a series of physical (hardware) and programming (software) elements that are quite significant for the operation of the equipment.

Basically, the parts that are replaced make the computer operate like a different one from the one it used to , but… Is it really another computer, or is it the same computer with new parts?

2. Vehicle reconstruction

Sometimes, after an accident, some vehicles are quite damaged by the accident and are repaired in almost all their parts. Repairing these vehicles involves replacing all damaged parts with new or used parts in good condition.

The questions that arise after the vehicle rebuilding process is completed are the same as in the previous example.

3. Sale of commercial premises

When a commercial property is sold, usually almost everything is changed; the staff, the infrastructure, and sometimes even the name .

But if trade continues to do the same thing as before, the questions we already know arise in the same way.

4. The human body

Human beings are long enough that virtually all their cells are replaced several times by younger generations.

Proposed solutions

The famous philosopher Aristotle proposes to give a definitive solution to the questions proposed by the paradox of Theseus’ ship, differentiating between the different types of causes.

1. Formal design

As long as one thing keeps its formal design, i.e. it continues to look the same, it is still the same thing .

2. Material cause

If an object keeps its initial material , that is, it is not reconstructed with pieces of another material, no matter if these are new or not, it can still be considered the same object.

3. Final cause

The final cause consists of the purpose for which the object has been made . As long as a body or object, however reconstructed it may be, still has its final cause (the purpose for which it was designed), it will remain the same initial object.

4. Efficient cause

This last consideration of Aristotle proposes that as long as the methods used in the repair and replacement of the parts of an object are done following the protocol stipulated for it, the object remains the same as before, only with modifications designed for it.

Definition of “the same”

Finally, it is important to understand that the definition of “the same” is something completely subjective, because for some people it may be the same to have two exactly the same bicycles stored in their garage, but for the most puritanical people this idea would not be valid.

Bearing in mind that there cannot be two bikes occupying exactly the same physical space anywhere even if the bikes are identical, they would have one characteristic that the other cannot share : the physical space occupied will never be the same.

Bibliographic references:

  • Aristotle (2008). Metaphysics. Editorial Alliance.
  • Cohen, S. M. (2004). Identity, Persistence, and the Ship of Theseus.