Cultures and civilisations rise and fall in a cyclical nature. Over time, many civilisations have conquered and then collapsed. Sociologists, anthropologists and religious advocates have preached this for centuries. Historian Ibn Khaldun was a key figure in the proposal of the theory, suggesting that empires will rise and fall via eight stages. These range from bondage and spiritual growth, to courage, to liberty, to abundance, to complacency, to apathy, to dependence, back to bondage. The major theme of the theories of rise and fall in societies is the Church and the biblical culture, which remain constant, although often in need of reform.