Psychoanalytic categories such as "neurosis", "psychosis", "mania", and "fixation" have become part of our everyday psychological vocabulary and we now routinely interpret states of anxiety, excitement, or depression in terms of physiological factors involving levels of serotonin, adrenalin, or blood sugar. To say that the characterization of thinking has a normative function that is irreducible to neurophysiological processing is not to say that our extant classification of the forms of thinking is incorrigible.