Darwin's book The Expression of the Emotions in Man and Animals, is among the most enduring contributions from 19th century psychology. The ideas expressed in its pages have persisted, for better or worse, down through the present, in one form or another. Although premised on an unsupportable interpretation of the nature of "expression," it is this idea that permeates the majority of work on emotional experience within psychology. It deals almost entirely with emotional display, but assumes a great deal about the nature of what is being displayed.