Living things are autonomous agents distinguished from nonliving things in having the purpose to actively maintain their existence. All living things, including single-celled organisms, have certain degrees of freedom from physical causality to choose their actions with intentions to fulfill their purpose. This circumstance is analogous to that of human intention-actions guided by mind, and points to the ubiquitous presence of the dimension of mind in the living world. The primordial form of mind in single-celled organisms eventually evolved into the human mind by virtue of the adaptive value of mind for survival. Life seems to have originated from nonliving matter in processes that are continuous. Thus the dimension of mind must extend to the nonliving world, and the origin of mind should be taken to relate to the origin of matter. Inasmuch as matter exists in a hierarchy of levels of complexity extending from quarks up to the whole universe, mind must also be presumed to exist in a hierarchy of levels of complexity associated with matter.