In the beginning there was logic

 I recently read an article in Philosophy Now (Issue 154, Feb/Mar 2023), jointly written by Owen Griffith and A.C. Paseau, titled One Logic, Or Many? Apparently, they’ve written a book on this topic (One True Logic, Oxford University Press, May 2022).
 
One of the things that struck me was that they differentiate between logic and reason, because ‘reason is something we do’. This is interesting because I’ve argued previously that logic should be a verb, but I concede they have a point. In the past I saw logic as something that’s performed, by animals and machines as well as humans. And one of the reasons I took this approach was to distinguish logic from mathematics. I contend that we use logic to access mathematics via proofs, which we then call theorems. But here’s the thing: Kurt Godel proved, in effect, that there will always be mathematical ‘truths’ that we can’t prove within any formal system of mathematics that is consistent. The word ‘consistent’ is important (as someone once pointed out to me) because, if it’s inconsistent, then all bets are off.
 
What this means is that there is potentially mathematics that can’t be accessed by logic, and that’s what we’ve found, in practice, as well as in principle. Matt Parker provides a very good overview in this YouTube video on what numbers we know and what we don’t know. And what we don’t know is infinitely greater than what we do know. Gregory Chaitin has managed to prove that there are infinitely greater incomputable numbers than computable numbers, arguing that Godel’s Incompleteness Theorem goes to the very foundation of mathematics.
 
This detour is slightly off-topic, but very relevant. There was a time when people believed that mathematics was just logic, because that’s how we learned it, and certainly there is a strong relationship. Without our prodigious powers of logic, mathematics would be an unexplored territory to us, and remain forever unknown. There are even scholars today who argue that mathematics that can’t be computed is not mathematics, which rules out infinity. That’s another discussion which I won’t get into, except to say that infinity is unavoidable in mathematics. Euclid (~300 BC) proved (using very simple logic) that you can have an infinite number of primes, and primes are the atoms of arithmetic, because all other numbers can be derived therefrom.
 
The authors pose the question in their title: is there a pluralism of logic? And compare a logic relativism with moral relativism, arguing that they both require an absolutism, because moral relativism is a form of morality and logic relativism is a form of logic, neither of which are relative in themselves. In other words, they always apply by self-definition, so contradict the principle that they endorse – they are outside any set of rules of morality or logic, respectively.
 
That’s their argument. My argument is that there are tenets that always apply, like you can’t have a contradiction. They make this point themselves, but one only has to look at mathematics again. If you could allow contradictions, an extraordinary number of accepted proofs in mathematics would no longer apply, including Euclid’s proof that there are an infinity of primes. The proof starts with the premise that you have the largest prime number and then proves that it isn’t.
 
I agree with their point that reason and logic are not synonymous, because we can use reason that’s not logical. We make assumptions that can’t be confirmed and draw conclusions that rely on heuristics or past experiences, out of necessity and expediency. I wrote another post that compared analytical thinking with intuition and I don’t want to repeat myself, but all of us take mental shortcuts based on experience, and we wouldn’t function efficiently if we didn’t.
 
One of the things that the authors don’t discuss (maybe they do in their book) is that the Universe obeys rules of logic. In fact, the more we learn about the machinations of the Universe, on all scales, the more we realise that its laws are fundamentally mathematical. Galileo expressed this succinctly in the 17th Century, and Richard Feynman reiterated the exact same sentiment in the last century.
 
Cliffard A Pickover wrote an excellent book, The Paradox of God And the Science of Omniscience, where he points out that even God’s omniscience has limits. To give a very trivial example, even God doesn’t know the last digit of pi, because it doesn’t exist. What this tells me is that even God has to obey the rules of logic. Now, I’ve come across someone (Sye Ten Bruggencate) who argued that the existence of logic proves the existence of God, but I think he has it back-to-front (if God can’t breach the rules of logic). In other words, if God invented logic, ‘He’ had no choice. And God can’t make a prime number nonprime or vice versa. There are things an omnipotent God can’t do and there are things an omniscient God can’t know. So, basically, even if there is a God, logic came first, hence the title of this essay.