Wuwei is an important concept in Taoism that literally means non-action or non-doing. In the Tao te Ching, Laozie explains that the beings or phenomena that are wholly in harmony with the Tao behaving in a completely natural, uncontrived way. As the planets revolve around the sun, they "do" this revolving, but without "doing" it. As trees grow, they simply grow without trying to grow. Thus, knowing how and when to act is not knowledge in the sense that one would think, "now I should do this," but rather just doing it, doing the natural thing. The goal of spiritual practice for the human being is, according to Laozi, the attainment of this natural way of behaving.