The right is always the party sector associated with the interests of the upper or dominant classes, the left the sector expressive of the lower economic or social classes, and the centre that of the middle classes. Historically this criterion seems acceptable. The conservative right has defended entrenched prerogatives, privileges and powers; the left has attacked them. The right has been more favorable to the aristocratic position, to the hierarchy of birth or of wealth; the left has fought for the equalization of advantage or of opportunity, for the claims of the less advantaged. Defence and attack have met, under democratic conditions, not in the name of class but in the name of principle; but the opposing principles have broadly corresponded to the interests of the different classes.