So, in my previous post, I talked about looking at ‘time’ in relation to a spatial dimension and hence arose the concepts of Four-dimensionalism and Three-dimensionalism. This post will consider a little more about these concepts.
Four Dimensionalism
Let’s start with four-diemensionalism. What exactly is its premise?
Well, its basic premise is that ‘time; can be treated as a spatial dimension and consequently that it is the 4th dimension (hence its name) with the 3 earlier dimensions being spatial ones, you know: height, width, and length.
There are two types of Four-dimensionalists (people who believe in four-dimensionalism) namely the Perdurantists and Exdurandists. The main difference between these two concepts is the admission of ‘temporal parts’. In this post, I will only consider the concept of perdurantism and four-dimensionalism may be used interchangeably with perdurantism.
What are ‘temporal parts’?
To understand the notion of temporal parts, we need to assume the ideology of the Perdurantists. Think; there are four dimensions: height, width, length and time <h,w,l,t>. This means that every point in the universe is defined by a unique permutation of these 4 variables. Let’s now try and define these four variables for an object: a coffee mug. To define the first three dimensions, we can simply look at the volume of the mug: 11 oz. Now for the fourth dimension, let’s say we say it is 8 am (for the purpose of the thought experiment consider that universe to be constricted to one day, hence ‘8am’ is a sufficient description of time). So, the mug is at <11oz, 8am>. Consider the mug an hour later, it is now defined by the same volume but at 9am. So the mug is at <11oz, 9am>.
Temporal parts are each of these descriptions: <11oz,8am> is one temporal part of the mug whereas <11oz, 9am> is another temporal part of the mug. Also note, that perdurantists wouldn’t call either of these as the object ‘mug’; The mug itself is a collection of all of its temporal parts: a set of all temporal parts.
Space-time worms and Block-Universe theory
From the above thought experiment, we can see how every object is some sort of a four-dimensional worm which extends through time. The mug you see at the present moment in time is not a whole object; it is only a part of the whole. We can also gather the admission of a block universe theory in which the whole universe is a four-dimensional blob because the ‘whole’ universe is the complete set of its temporal parts at all ‘Time’.
Why do we call an object in four-dimensionalism a ‘worm’?
The cube represents the block universe. Each dot represents a singular temporal part of some object. Notice when all of its temporal parts are put together, the object looks like a tiny little worm?
Three dimensionalism
Of course, there is the competing view of Three-dimensionalism which essentially is just the common-sense view that objects are simply just three-dimensional (like we’re used to them being) and that they just exist through time. So any object at a particular time is the whole object itself. Nothing special here, just what we all already believe.
So which is the correct view?
If I could answer that question, I’d get a Nobel prize or something. Sadly, I can’t. While Four-Dimensionlism solves a heap of metaphysical questions such a the problem of identity and while it is in-line with modern physics such as the Einstein’s theory of relativity, it comes with its own set of paradoxes such as how it essentially makes ‘change’ illusory and objections to the very consideration of ‘time’ to be a ‘space’-like dimension.
That’s it for this post
Till Later!
References:
Sider, T. (2001). Four-Dimensionalism. doi:10.1093/019924443x.001.0001
Hawley, K. (2020, May 05). Temporal Parts. Retrieved July 15, 2020, from https://plato.stanford.edu/entries/temporal-parts/
What are Temporal Parts? (Perdurantism and Endurantism Definition) [Video file]. (n.d.). Retrieved from https://www.youtube.com/watch?v=77gGQ0cc9oE
Ludwig, Kirk. “Time.” Online lecture, April 23, 2020.
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