Historian of psychology Mark Altschule concluded , `` It is difficultâ '' or perhaps impossibleâ '' to find a nineteenth-century psychologist or psychiatrist who did not recognize unconscious thought as not only real but of the highest importance '' . Yet , as historian of psychology Mark Altschule concluded , `` It is difficultâ '' or perhaps impossibleâ '' to find a nineteenth-century psychologist or psychiatrist who did not recognize unconscious cerebration as not only real but of the highest importance . ''