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> how to use it outside of the logic domain You've got it backwards. Logic isn't a domain, just like algebra isn't a domain. Logic is what lets us work within

> how to use it outside of the logic domain You've got it backwards. Logic isn't a domain, just like algebra isn't a domain. Logic is what lets us work within a given domain. It isn't like geometry, which won't be useful unless you're working with shapes and angles; logics (and, more generally, algebras) are the syntax of entity relations. In particular, logic is about "preserving truth between statements". That is, if we have a set of true statements, and we want to generate new true statements, logic is the way to do that, and it's always done in the same way, using arguments. That word has two common meanings, but the arguments of logic are: premises, linked by deductive rules to conclusions. If the deductive rules are valid, and the premises are true, then the conclusions will deductively also be true. "Premises" can be any type of statement that has a truth-value (i.e. makes a claim about a fact). So, obviously, this is the basis of all proofs, in any discipline. But it's also the foundation of rational persuasion, as in a court room. Which is to say that you're already using informal logic, every day. The question is "would it be useful in your life to learn these things formally?" What's the difference between someone with the intuition "the opposite side of the 90° angle in a triangle is always the largest", versus someone who understands the Pythagorean theorem?

skybrian 4y ago
But how do you know that "informal logic" has anything to do with formal logic? Outside of math, formal logic seems actively misleading. For example, the "principle of explosion" (from a contradiction follows anything) is definitely not how people think. Philosophically, I prefer the reasonable / rational / meta-rational framework explained by David Chapman. [1] But if you want to know how people ordinarily think, better to study how they think. (And in practical everyday use on the Internet, I find logic mostly useful for for shooting down attempts at inappropriately applying logic to conclude things that you can't safely conclude.) [1] https://metarationality.com/reasonableness-aspects https://metarationality.com/reasonableness-aspects
- IIAOPSW 4y ago
  >the "principle of explosion" (from a contradiction follows anything) is definitely not how people think. "Well then, if you believe that then you'll believe anything." Sounds pretty folksy to me.
- thaumasiotes 4y ago
  > Outside of math, formal logic seems actively misleading. For example, the "principle of explosion" (from a contradiction follows anything) is definitely not how people think. It's generally very easy to find natural language constructs that rely on any given principle of formal logic. For the principle of explosion, an example would be "if you're thirsty, there's tea in the kitchen".

skybrian 4y ago

But how do you know that "informal logic" has anything to do with formal logic? Outside of math, formal logic seems actively misleading. For example, the "principle of explosion" (from a contradiction follows anything) is definitely not how people think. Philosophically, I prefer the reasonable / rational / meta-rational framework explained by David Chapman. [1] But if you want to know how people ordinarily think, better to study how they think. (And in practical everyday use on the Internet, I find logic mostly useful for for shooting down attempts at inappropriately applying logic to conclude things that you can't safely conclude.) [1] https://metarationality.com/reasonableness-aspects https://metarationality.com/reasonableness-aspects

IIAOPSW 4y ago
>the "principle of explosion" (from a contradiction follows anything) is definitely not how people think. "Well then, if you believe that then you'll believe anything." Sounds pretty folksy to me.
thaumasiotes 4y ago
> Outside of math, formal logic seems actively misleading. For example, the "principle of explosion" (from a contradiction follows anything) is definitely not how people think. It's generally very easy to find natural language constructs that rely on any given principle of formal logic. For the principle of explosion, an example would be "if you're thirsty, there's tea in the kitchen".