The original meaning of su (素) is undyed natural colored silk. Pu (朴) refers to unprocessed wood. The extended meaning of the term is humans or anything that is in a basic, natural state or condition. The opposite is anything that is artificially altered or interfered with. Scholars of the Daoist school held that a ruler should protect the natural state of his subjects through non-action and avoid interfering too much with their lives. However, scholars of other schools maintained that the natural state of both humans and objects must be changed and molded in order to be of use.

In the best times when virtue prevailed, when all creatures and things lived together, it was hard to tell which man was virtuous or petty. When all were without knowledge, virtue would not be violated. When all were in their natural state, people could retain their basic nature. (Zhuangzi)