Actually
IQ=(mentalAge/physicalAge)*100
You don't really "come up" with it. IQ is a valid way to measure the worth a person quickly.
As are standardized tests.
The notion of a logic-driven society doesn't make any sense to me. I don't understand what you mean at all. Are decisions made... logically? From what premises are the logical reasonings made? It sounds to me like the only thing different from your idea of a right society from others' is that its logic is derived from the arbitrary axioms that you prefer, while others' are derived from different premises regarding righteousness. Would your society, by any chance, restrict mating to once every seven years?
If you break down all information into bits, there is clearly a "wrong way" and a "right way". In an ideal society
the "perfect" person would just be cloned over and over again to make up the whole society and brought up in exactly the same environment. In this way, war nor conflict would exist.