Historian Toynbee tells us that revolution occurs when the existing structure of "Society", has ceased to answer to the conditions, needs and demands of Society which has the power to make a change in the structure. In recorded history, changes brought about by revolution have brought about changes in the management of Society along with new conditions, needs and demands which put new tensions on Society. Within the period from which records survive, we have evidence that there have been many revolutions. Over time, revolutions have become more frequent. Toynbee further tells us that evolution has been the rule for betterment of Society, and revolution has been the exception.