I think perhaps a better example would be the difference between partitive and quotative division.
Maybe even easier example is the commutativity of multiplication itself. It is not a priori clear that 5 group of 3 objects each are the same as 3 groups of 5 objects each. When I was a child I was feeling confused why addition and multiplication are commutative while exponentiation isn’t.
I’m going to some lengths to point this out because the idea of math as perfect and axiomatic just isn’t the mathematics that humans practice or know. It can look that way, but the truth seems to be more complicated than that.
Yes, we have powerful (sometimes astoundingly powerful, as in case of Ramanujan) intuitions built in our brains that allow us to do high-level operations. Mathematics is practically never done on the lowest level of formal manipulation. There is certainly large difference between mathematics as an axiomatic system and the art of mathematics as a human endeavour—if there weren’t, mathematicians were replaced by machines long ago. But that doesn’t seem much relevant to the question of truth of mathematical theorems. Whatever intuitive thought had lead to its discovery, people will agree that it is valid iff there is a formal proof.
Maybe even easier example is the commutativity of multiplication itself.
That’s a good point! I avoided that example because there’s a pretty easy and convincing “proof” of the commutativity of multiplication, namely that turning a rectangle on its side doesn’t change how many things constitute it So, it doesn’t matter whether you count how many are in each row and then count how many rows there are, or if you do that with columns instead.
I think it’s terribly sad that they don’t encourage children to notice that or something like it. But there are a lot of things about education I find terribly sad and that I’m doing my damnest to fix.
But that doesn’t seem much relevant to the question of truth of mathematical theorems. Whatever intuitive thought had lead to its discovery, people will agree that it is valid iff there is a formal proof.
Agreed, though there’s no objective definition of what constitutes a “formal proof”. Despite what it might seem like from the outside, there’s no one axiomatic system and deductive set of rules to which all subfields of mathematics pay homage.
Maybe even easier example is the commutativity of multiplication itself. It is not a priori clear that 5 group of 3 objects each are the same as 3 groups of 5 objects each. When I was a child I was feeling confused why addition and multiplication are commutative while exponentiation isn’t.
Yes, we have powerful (sometimes astoundingly powerful, as in case of Ramanujan) intuitions built in our brains that allow us to do high-level operations. Mathematics is practically never done on the lowest level of formal manipulation. There is certainly large difference between mathematics as an axiomatic system and the art of mathematics as a human endeavour—if there weren’t, mathematicians were replaced by machines long ago. But that doesn’t seem much relevant to the question of truth of mathematical theorems. Whatever intuitive thought had lead to its discovery, people will agree that it is valid iff there is a formal proof.
That’s a good point! I avoided that example because there’s a pretty easy and convincing “proof” of the commutativity of multiplication, namely that turning a rectangle on its side doesn’t change how many things constitute it So, it doesn’t matter whether you count how many are in each row and then count how many rows there are, or if you do that with columns instead.
I think it’s terribly sad that they don’t encourage children to notice that or something like it. But there are a lot of things about education I find terribly sad and that I’m doing my damnest to fix.
Agreed, though there’s no objective definition of what constitutes a “formal proof”. Despite what it might seem like from the outside, there’s no one axiomatic system and deductive set of rules to which all subfields of mathematics pay homage.