Reductio Ad A Tape Measure

Can the humble tape measure be used to understand the reductio ad absurdum involved in the cosmological argument. 


So, a couple of weeks ago, my dad was playing with a tape measure by seeing how far the metal tape ruler could reach without breaking. As I watched the multiple failed attempts, I couldn’t help but say, 
“What a beautiful metaphor for the cosmological argument.” 
Dad just looked at me; my family love philosophical debate, particularly my dad, but even this was a step too far. However, I couldn’t help but see how far I could push this metaphor. 
A lot of cosmological arguments depend on using reductio ad absurdum to disprove the idea of infinite regress as a step in proving that God created the universe. That is to say, the idea that the universe has always existed must be false so something must have caused the universe. An example of this is Aquinas’ first way.
The argument states that some objects are in a constant state of motion. For example, wood is changing from being a branch to being ash in a fire. However, nothing can be moved or changed by itself; wood doesn’t spontaneously combust by itself. Something must have caused it to catch on fire. There are two options for this cause; a primary mover (something that can move itself and others without being moved itself) or a secondary mover (something that can move itself and others only once it has been moved itself). Everything within this world is a secondary mover, so we can trace the chain back through cause and effect. At this point, we have two options; either the chain goes infinitely back via secondary movers (known as infinite regress) or we eventually get to a primary mover which caused the chain. However, infinite regress is proved false via reductio ad absurdum as if there was no primary mover, then there would be no secondary movers as nothing would have caused the chain. This is clearly wrong, as we can see the chain of secondary movers within the world. Therefore, there must be a primary mover which caused the existence of the universe, who Aquinas labels “God”.
So how does a tape measure fit in to the cosmological argument? Well, it demonstrates why there can not be an infinite chain of secondary movers. Imagine that the metal ruler is the chain of secondary movers. No matter how hard you try, you would not be able to stop the metal ruler from breaking, let alone if the chain went on for infinity. Therefore, like the tape measure, there must be something supporting/causing the chain of secondary movers, demonstrating Aquinas’ reductio ad absurdum above. 
However, Mackie would suggest that Aquinas had the wrong idea about the chain of secondary movers and that he was confusing a very long chain with an infinite one. To demonstrate this, he uses a chain of hooks going vertically upwards. If it was just a long chain of hooks, then indeed at some point there would be something supporting the chain, such as an attachment to a wall. However, this would not be the case if there was a chain of infinite regress as there would be no beginning and no end to the chain, otherwise it would go into the category of a very long chain. Therefore, it could be argued that a chain of infinite regress needs no cause and it still remains a possibility, defeating the point of the cosmological argument. 
Despite this, we can still argue for the cosmological argument because of scientific evidence that shows there was a start to the universe. For example, Einstein’s Theory of Relativity, Hubble’s discovery of red shift, and CMB radiation.  These clearly show that the universe is expanding leading to the conclusion that there was a “Big Bang” that created the universe (hence the name the Big Bang Theory). If this was the case, then there must be a cause as it is a very long chain. 
Even so, can we really use a tape measure as a metaphor for reductio ad absurdum? There are some issues which we can’t ignore. For example, the metal part of the tape measure is not a chain, it is a continuous piece of metal and therefore cannot be used to represent the cause and effect of secondary movers. However, it could be argued that if we had a chain of hooks in Mackie’s example, then it would still not be able to support itself and so the use of a tape measure instead of a chain doesn’t really impede our understanding of the cosmological argument. 
A more pressing matter is whether we can compare an object that is within time and space to the idea of events that link together to create time. When it comes to the tape measure, the tape measure has to abide to natural laws that govern the external world. The reason why the tape measure can’t support itself is because it is pulled down by gravity, a rule of the world. Therefore, it is possible (although not certain) that time can support itself due to the nature of time. However, this can’t be certain due to our limited knowledge of time. 
In conclusion, a tape measure can be used to represent the cosmological argument as it demonstrates how infinite regress is false because it cannot support itself without having a primary mover. However, this metaphor, along with the cosmological argument, does have it’s flaws, such as the dependence of the tape measure on the laws of nature.

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Published by Philosopher Ad Absurdum

Student studying MA Philosophy of Mind and Cognitive Science at the University of Birmingham; First Class BA Philosophy and History from the University of Southampton.

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