The 3rd and 4th centuries saw the rise of the "Xuanxue" (mysterious learning), also called "Neo-Taoism". The most important philosophers of this movement were Wang Bi, Xiang Xiu and Guo Xiang. The main question of this school was whether Being came before Not-Being (in Chinese, "ming" and "wuming"). A peculiar feature of these Taoist thinkers, like the Seven Sages of the Bamboo Grove, was the concept of "feng liu" (lit. wind and flow), a sort of romantic spirit which encouraged following the natural and instinctive impulse.