In this post we are going to philosophically look at dimensions, in particular the 4th dimension. This discussion will also help solve an age-old philosophical problem: when are two things identical?
So, on what grounds can we define one thing being exactly the same as something else. Let’s say you have a black chair, but you decide to paint it yellow. Is it still the same chair? Or let’s say that you have an apple, you put it on your counter to rot for years. Eventually the apple will just be this little brown mush, looking like a plum or something. Is it still an apple then? If not, when did it stop being an apple?
These are problems relating to identity that have puzzled philosopher for more than 2 thousand years. Aristotle tried to solve this puzzle by saying that there are accidental changes to an object and essential changes. Accidental means that something trivial changes, like its color. So he would say that the chair painted yellow is still the same chair. But then there are changes that change the essence of a thing. For example, if you take a chair and remove the entire upper part, so that you only have 4 legs, well I think you successfully removed the essence of the chair. The point of a chair is for us to sit on. If you can’t do that, well, then it’s not really a chair anymore.
This is a nice attempt to solve the puzzle, but then the problem is, okay, how the hell are we supposed to know what is accidental and what is essential? How about the apple then, after rotting for half a year. It’s not edible anymore, but did it already lose its essence? At what point did it lose its essence then?
Same thing applies to a person. You look completely different than when you were a baby and you will look entirely different when you are at the end of your lifespan. And you are probably doing all sorts of stuff right now that are part of your identity, which you weren’t doing as a baby. 4-dimensionalism can help answer why we still call these versions of you identical.
The point of 4-dimensionalism s to start seeing time not anymore as this special mystical thing, but more like space in a sense. So, any thing does not only have three dimensions, length, width, and height, but also has time as a fourth dimension. Let’s take a human as an example.
You start out as a baby, you grow into an adult, and then eventually become a senior. 3-dimensionalists would say the baby is you, the adult is you at a later time, and finally, the senior is you but again at a different time. 4-dimensionalists say the entire thing is you. You are this entire thing stretching from begining to end. You basically stretch out towards through time as a sort of 4-dimensional worm. Same thing with any other thing, it is too a 4-dimensional spacetime worm.
You might be thinking why on earth we would want to think of such a theory. One day I’m a human, and the next day I’m an interdimensional spacetime worm. Well, actually, this philosophical perspective is what comes closest to our understanding of modern physics today. In the 20th century Einstein came along and said: you know what, time and space are not so different after all. He unified space and time together, into well… spacetime (physicists aren’t really known for their original names). Anyway, we can regard our environment more as a sort of 4-dimensional space, and it turns out that we can describe the laws of the universe much better if we view it in this way.
So, time and space are already unified in physics, now we want to know what kind of consequences this has for philosophy, in particular the branch of philosophy known as metaphysics. And it turns out, that this is useful to describe how identity can stay the same, even though things in the world take many different shapes throughout their life spans.
Different Flavors of 4-Dimensionalism
Now, there are two different flavors of 4-dimensionalism. Then one I described above, about you being a 4-dimensionl spacetime worm, is called perdurantism. You are the entire thing, and you as a baby, or as an adult are just parts of the entire thing. More specifically, they are called temporal parts. So basically, your “time parts”.
There is another theory which is called exdurantism or stage theory which argues that you are just a complete being when you are a baby or an adult, but that you have a special type of relationship with your other selves in time. These are called temporal relationships.
Please let us know if you follow the viewpoint of perdurantism, exdurantism, or just regular ol’ 3-dimensionalism which is also called endurantism. That one says that you are just a 3-dimensional being which somehow persists through time.