In societies stratified into classes, upward mobility is hindered by not acquiring the behavioural characteristics of the class above. All these characteristics comprise an unwritten rule book. The 'chapters' include, for example, conversational behaviour, manner of speech, physical deportment, attire, hygiene and grooming, manner of eating and choice of food and beverages. There are also norms for personal possessions, recreations, cultural interests and ethical and political viewpoints. Failure to comply with any standard in the unwritten code stigmatizes an individual as not a true member of the class and can lead to social ostracism on that level. The unwritten code is a fossil from feudal times and is a tool for social repression.
Written codes produce legalistic, literal, and minimal compliance with the letter and not with its spirit. Unwritten codes, of honour, of trust, of loyalty and of all decent behaviour are both the ideal and the inspiration that raises the quality of any society.