Limits... seem to me of two kinds, ordinary or natural, and extraordinary or beyond the natural. The first limits comprise within them the qualities which deviate more or less from the mean, without attracting attention by excess on one side or the other. When the deviations become greater, they constitute the extraordinary class, having itself its limits, on the outer verge of which are things preternatural... We must conceive the same distinctions in the moral world.

Preface of M. Quetelet - A Treatise on Man and the Development of His Faculties (1842)