As he wrote in the introduction to Hereditary Genius: I propose to show in this book that a man's natural abilities are derived by inheritance, under exactly the same limitations as are the form and physical features of the whole organic world.
Como escribiu na introdución de O xenio hereditario: Propóñome mostrar neste libro que as habilidades naturais do home derivan da herdanza, baixo exactamente as mesmas limitacións en que o son as características físicas de todo o mundo orgánico.