Date: Dec 2, 2012 9:58 PM
Author: Jonathan Crabtree
Subject: Re: Some important demonstrations on negative numbers

> >I have also provided a precise verbal mapping of the
> instructions that reveal the logic of why the
> products of both -ve x - and - x -ve are positive.
>
> Perhaps you can rationalize it - you can't prove it
> in the mathematical sense without making prior
> assumptions.


Hi Joe

Just letting you know I use the same verbal logic as John Wallis, credited as the inventor of the number line.

QUOTE

Even the rule of signs was but a consequence of "the true notion of (arithmetic] Multiplication [which] is ... to put the Multiplicand, or thing Multiplied (whatever it be) so often, as are the Units in the Multiplier."

>From the latter definition Wallis argued consecutively that

a) multiplication of a negative multiplicand and positive multiplier involved no more than taking the multiplicand the specified number of times, and thus getting a negative sum;

b) multiplication of a positive multiplicand and a negative multiplier involved nothing more than taking the multiplicand away the specified number of times; and, finally,

c) multiplication of a negative multiplicand and a negative multiplier involved "taking away a Defect or Negative," which "is the same as to supply it" ? and thus getting a positive."

NOTE: My lettering for clarity.

SOURCE: Symbols, Impossible Numbers, and Geometric Entanglements. by Helena M. Pycior