Normal is a concept that stems from two very interesting mathematical concepts: the normal distribution and the central limit theorem. People possess infinite numbers of properties. By far the most are unknown, they don’t matter to our reality. However, through our knowledge systems - perception and thinking - we transform infinite into finite: height, weight, intelligence, kindness, wealth, strength etc. The sum of a large number of independent variables forms a normal distribution again. Human sciences are often hide the fact that distributions are side effects of mathematical descriptions of traits. Every person can also be described in qualities in which (s)he belongs to the absolute top (and minimum). However, probably humanity isn 't interested in those distributions in which you achieve the top. But then again, being neurotic, being rich, or being intelligent according to an IQ test is ultimately also arbitrary.