“Individuals are types of themselves and enslavement to conventional names and their associations is only too apt to blind the student to the facts before him. The purely symptomatic forms of our classifications are based on the expressive appearances that insanity assumes according to the temper and pattern of the subject whom it affects. In short, individual subjects operate like so many lenses, each of which refracts in a different angular direction one and the same ray of light.”

William James, cited by Eugene Taylor, The 1896 Lowell Lectures