²⁰To non-theorists, this notation may be slightly confusing; the inequality relations in 1) and 3) are taken to mean ‘for any specific element $∙$ in the domain of the functions in question’ so that, e.g., $x≤ y$ is short for $x(∙)≤ y(∙) ∀ ∙ ∈A.$ In this notation, $ζξг$ in 3) is a function which can be applied to any argument $∙$ (because $г$ is a function).