OK, I might sound like a pretentious ass–heck, I might even be a pretentious ass–but I’m just trying to save you from looking like a fool. Well, to be entirely accurate, I’m trying to save myself from aggravation, but I’m trying to save my self from the aggravation of watching you look like a fool, and logically, that benefits both of us, right?
So here’s the thing: the word “logical” is often used as a synonym for “rational” or “reasonable”, and I don’t have any objection to that because it’s common usage, and well understood. But when you use the word “logic” as a noun to refer to a form of reasoning, and you don’t know any of the literature behind the word, you are practically guaranteed to be saying something that sounds irritatingly stupid to people who are familiar with the literature.
Some words can be picked up from context. You don’t need to look up “wack” when you hear it in this context, “He thinks Elvis is still alive! He thinks a Jewish cabal ordered 9/11! He thinks he gets messages from aliens! He’s wack!” OK, first time I ever heard “wack” and I pretty much know what it means and how to use it in a sentence.
Other words are likely to be misunderstood if picked up entirely from context; I imagine that’s how “awful” came to mean the opposite of “awesome” when it originally meant the same thing. Something that provokes great awe can be frightening or exhilarating (or both). Most likely the word “awful” tended to be used in more frightening contexts while the word “awesome” tended to be used in more exhilarating contexts, until people, going from context, came to understand them as opposites.
“Logic” is one of those prone-to-misunderstanding words. Hearing it in context, you are likely to think it means something like “the process of rational thought” or “not making mistakes in your reasoning”. You may even pick up on the idea that there are rules of rational thought, and that is even worse, because you may assume you can make up whatever rules you like and claim that they are “logic”.
This is why, I suspect, one so often sees random internet blowhards holding forth ignorantly on the topic of logic: what logic says, what logic requires, what logic assumes, when it is clear that other than hearing the word used by others they have no idea what logic is. It’s like listening to someone whose entire knowledge of mathematics is based on second-grade arithmetic, trying to educate you by explaining that you can’t add one number to another and get a smaller number–adding two number always makes a bigger number!
So when someone tells you that “logic” says you should base base your beliefs on experience, or “logic” says that you should not rely on authority, then you know their idea of logic came from Mr. Spock and not from any logician. I’m not saying that you shouldn’t base your beliefs on experience; I’m saying that’s not what logic is about. Logic doesn’t tell you what to believe or how to form beliefs; it tells you, given a set of premises, how to distinguish good reasoning from bad reasoning. Where you get your premises and what you should believe is another field called epistemology. Even the conclusions you come to are not part of logic.
So here is the simple truth: if you don’t know the Law of Identity, the Law of the Excluded Middle, the Law of (non-)Contradiction, and the Law of Modus Ponens, you should not be holding forth on logic. If you can’t define “proposition”, “predicate”, “logical connective”, “quantifier”, and “truth value”, you should not be holding forth on logic. If you don’t know the difference between the form and the content of an argument, or the difference between deduction and induction, you should not be holding forth on logic. If you don’t know those things, the odds that you will say anything about logic that is not obviously false are minuscule. And if you only know those things because you read this article and looked them up on Wikipedia, you still don’t understand logic well enough to discuss it in public. Please save yourself the risk of looking foolish and save me the aggravation.
There are alternatives! You can be as much of a blowhard as you want without looking like an idiot by holding forth on a topic you know nothing about. Instead of saying that “logic says you should base your beliefs on experience”, say “it is irrational not to base your beliefs on experience”. Instead of claiming that logic says you should not rely on authorities, say “It is irrational to rely on authority”. Of course, if you said that, you would be wack, but at least you didn’t say something foolish about logic.