People in later generations often condemn the sexual indulgence in ancient societies, deeming it as a prevailing immoral trend. For instance, some historians believe that the immoral trend and the Romans' lust were one of the key reasons for the fall of the ancient Roman Empire. Likewise, scholars of Daoism in later generations in China frequently scolded the "lewd Tang and licentious Han" dynasties, also because of the relatively open sexual attitudes during the Han and Tang periods in Chinese history.