Philosophy Articles #4-The Ship of Theseus

It is also important to note that many other questions arise out of the concepts of identity and essence. One set of such questions regards how identity factors into relationships between objects. For example, if two objects are identical (therefore are the same thing), will they always be immutably and unchangeably identical? The reasoning behind this question comes from the idea that for two objects to be truly identical, they must have absolutely no differences. This means that if the two objects experience two different sets of experiences, they are different and thus no longer identical. As a matter of fact, even being in a different position in space can change the identity of the objects. From this, we can conclude that an object can only really be identical to itself, as no other object can be the exact same, as no other object can occupy the same time and space constraints, among many others.

But perhaps the most famous question regarding identity and essence is the one posed by the thought experiment called the Ship of Theseus. This thought experiment dates back many centuries, all the way back to the ancient Greeks, where it was discussed by the philosophers Heraclitus (circa 535 BCE-475 BCE) and Plato (circa 428 BCE-347 BCE). The thought experiment revolves around a ship that the Greek mythological hero Theseus sailed. Say that the ship, due to many years of use, begins to rot. Slowly, the planks and various parts of the ship are replaced by new ones. After many years, every single part has been replaced. The question now is: Is the ship in its current state the original ship of Theseus?

One answer is that the ship is not, because each individual instance of the ship is a different ship. This reasoning claims that time is a property that acts upon the ship, and therefore the ship is constantly changing, because time is constantly moving forwards. As time moves forwards, the ship’s property of time changes and so its identity is changing with it. So, there are an infinite amount of instances of the ship, all different because of the different times at which they exist.

Another answer claims that the ship is the same, based off the idea that identity trumps essence. This reasoning starts from the basis that the essence of an object is not as important as the identity of the object in determining what it is because essence is only a part of the identity. This claims that each property has a level of importance, and if a majority of the importance is unchanged, than the object remains unchanged. Therefore, the object’s properties can change without the object actually changing. For example, water molecules can be rigidly packed together into ice or sparsely separated like vapor, but fundamentally all remain the same water, because the atoms of an object are a very important aspect. Thus, for the ship, this answer would suggest that because the ship still serves the purpose of a ship, is ship-shaped, and has all the components of the original ship, it is the same ship, just with some changed properties.

A third argument denies the existence that there is even a ship! In this argument, the ship is just a mass of atoms arranged in a fashion that humans have conceptualized as a ship. The ship after having all its parts replaced is another concept. The reasoning now is that the two concepts can be compared, and thus therefore must be different (because humans cannot compare something to itself).
Later, the English philosopher Thomas Hobbes (1588-1679) extended this problem. He claimed that the ship would slowly lose its identity as each part was being replaced, until the last part had been replaced and so the ship was totally different. But he then proceeded to consider what would happen if all the replaced old parts of the ship were gathered together and built into a new ship. Would this second ship, constructed out of the old parts, be the same as the old ship?

And finally, we have the approach of the Austrian Ludwig Wittgenstein (1889-1951), who claims that many philosophical problems, including this one, are actually problems of language and semantics. Wittgenstein’s ideas revolved around the fallibility of language, and so his approach claims that words mean different things to different people; and thus the problem lies in different interpretations of these words.