#16
The idea that negative numbers don't exist (but ordinary positive numbers do) is all garbage philosophy and bullshit.
If you don't believe in negative numbers, you still can define relative numbers without any circular argument in the following way.
Let N the set of natural numbers; +,x denotes the usual operations.
A "relative number " is a subset X of N^2 (the set of pairs of numbers) having the following property:
there exist a pair (a,b) in X such that for every pair (c,d), (c,d) belongs to X if and only if a+d=b+c.
if X,Y are relative numbers in the above sense we define X+' Y as the set of all pairs (p+q,r+s) where (p,r) is in X and (q,s) is in Y. We also define X *' Y as the set of all pairs (p*q+r*q, p*r+q*s).
If n is an element of N we define f(n) as the set of pairs (k+n,k) where k is any natural integer.
Finally we say that the relative integer X is strictly smaller than the relative integer Y and we write X <' Y if for some (a,b) in X and (c,d) in Y, a+d < b+c (it turns out that when it is the case then for every(a',b') in X and (c',d') in Y,we also have a'+d' < b'+c').
If you're motivated you can check that
1°) if X and Y are relative integers, so are X +' Y and X *' Y.
2°) The set of relative integers with the operations +',x' defined as above is a ring with f(0) being neutral for the sum+' and f(1) neutral for the product x' (i.e usual algebraic properties hold)
3°) for every p q natural integers, f(p+q)= f(p)+' f(q) and f(p x q)= f(p) x' f(q)
4°) for every p, q natural integers, if f(p)= f(q) then in fact p = q ( 3° and 4° allow to view N as a subset of the set of relative integers with the same operations)
5°) <' is a total strict order and for every natural integers k l, k < l if and only if f(k) < f(l)
6°) for every X relative number, if by -'X we denote the set of all pairs (q,p) where (p,q) is in X, then -'X is also a relative integer and X + (-' X) = (- X')+ X = f(0). -'X is the only relative number to have this property.
7°) for every relative number Y, f(0) <' Y or Y= f(0) or Y <' f(0). Y <' f(0) if and only f(0) <' -'Y; and -'Y <' f(0) if and only if f(0) <' Y.
8°) if A,B are relative numbers A <' f(0) and B<' f(0), then f(0) <' A x' B (NB: so in that construction, the infamous fact that "the product of two negative numbers is a positive number" can be deduced).
The set of relative integers is usually abbreviated by the letter Z.
ok you defined a bunch of stuff and gave some definitions from modern algebra but forgot to state your conclusion.
@pdve
@Deirdreskye
absolutely! John Nunn has a Phd in topology and is a strong GM and incredible problem solver (the first chess book I 've ever bought - chess puzzle book - is from him. I loved this book
)