Full Idea
Things such as teeth and crops turn out as they do either always or usually, whereas no chance or spontaneous event does. ..So, given that these things cannot be accidents or spontaneous events, they must have some purpose.
Gist of Idea
Teeth and crops are predictable, so they cannot be mere chance, but must have a purpose
Source
Aristotle (Physics [c.337 BCE], 199b33)
Book Reference
Aristotle: 'Physics', ed/tr. Waterfield,Robin [OUP 1996], p.51
A Reaction
This is a good argument, and Darwin's theory does not destroy it. We have no idea why there is order, regularity and pattern in nature. Aristotle does not leap to a divine explanation. The 'purpose' of things might be non-conscious.