One Plus One Equals Two: More or Less

Abstract

This note discusses a range of cases where the proposition that one plus one is more or less than two makes sense. Simple examples from the natural world indicate that interaction (reproduction and predator-prey interaction) between addable units can change their sum. A case drawn from commerce documents an example for many similar circumstances where units have more than one dimension. The logical ambiguities described here can hamper human communications and are thus of interest for behavioral studies.