 Subtraction is a type of analysis called ordinal analysis

...let space be now regarded as the field of progression which is to be studied, and POINTS as "states" of that progression....I am led to regard the word "Minus," or the mark −, in geometry, as the sign or characteristic of analysis of one geometric position (in space), as compared with another (such) position.The comparison of one mathematical point with another with a view to the determination of what may be called their ordinal relation, or their relative position in space...