-To see the reality of final causality, one must see that certain effects follow from certain causes in a non-accidental way. Said another way, if you can look at an object or an action and determine what it is able to do in virtue of what it is, you have, at least implicitly, affirmed final causality.
-Final causality does not necessarily imply extrinsic purpose. In fact, since final causality is said mostly of nature, and nature is itself an interior power, most final causes have nothing to do with extrinsic purpose, deliberation, craft, or intention.
-Objection: Final causality does not exist in nature because nature sometimes produces defects.
Reply: Even a grammarian can misspell words. This does not eliminate either the grammatical science or the intent of the grammarian to spell correctly.