 The discussion about biological teleology has ancient origins. It is particularly prominent in Plato’s depiction of the divine Craftsman or ‘Demiurge’ in the  Timaeus  and Aristotle’s discussion of final causes in the Physics (see the section on teleology in the entry on  Aristotle).  However, Plato’s and Aristotle’s understanding of teleology, as well as their arguments for teleology in the natural world, are distinct (Lennox 1992; Ariew 2002; Johnson 2005). Whereas Plato’s teleology is anthropocentric and creationist, Aristotle’s is naturalistic and functional. On the Platonic view, the Demiurge is the source of all motion in both the heavens and on earth, and the universe and all living beings within it are artifacts modeled on the Forms (see the relevant sections of the entries on  Plato  and  Plato’s metaphysics).  The goal toward which all things, including living beings, are directed is the external and eternal good of the Forms. In contrast, on the Aristotelian view, the teleology that directs the behavior of living beings is immanent. For instance, in organismal development, the impetus for this goal-directed process is a principle of change within the organism, and the telos, or goal, of the development is also an inherent property. Although often conflated, the views of Plato and Aristotle on teleology have been influential in historical debates on biological teleology, and one can still find Platonic and Aristotelian ideas in the current debate on biological functions. 