Aristotle (384-322 B.C.) argues that all natural things have an end or purpose they are trying to consciously or unconsciously achieve. Nature is thus teleological: it is purposeful and all natural processes are undertaken for the sake of realizing essential or natural potentials (telos=end or purpose). This view of nature was by no means accepted by all thinkers in Greece. For example, Empedocles, anticipating Charles Darwin, claimed that processes are not for the sake of purposes. Rather, chance processes occur and some of these processes lead to forms that work and support life. These processes can be understood mechanistically without reference to purpose. Obviously Darwin’s vision has been widely accepted in the scientific community and their verdict is clear: Aristotle is wrong and nature is NOT teleological. But Aristotle argues that if chance were the ground of natural development then we wouldn’t have the consistent replication of forms that we do. Chance can only explain breaks from the norm: it cannot explain law-like activity. For example, we see that acorns do, for the most part, make oak trees if the proper conditions are present. To be sure, once in a while we have an aberration and an acorn produces some deformed object we can’t recognize as an oak. But that would be chance. If everything was a matter of chance, Aristotle would argue, we would never have millions of acorns producing millions of well-formed oaks on a regular basis.
For more on chance and law, go here.