Then defect is no longer intelligible. And yet, we can determine if a heart is defective, because we know the function of a heart, we know how that function com

Then defect is no longer intelligible. And yet, we can determine if a heart is defective, because we know the function of a heart, we know how that function composes into the telos of the organism (which is what transmits the function to organ, so to speak). Thus, any modification of the heart, certainly one that we see has ill effects for the organism, is a defect. It is clear that a human being who is sterile, or one who cannot move about, is in some sense a defective specimen, as these deficiencies impede the realization of human telos. (If you deny telos, then truly nothing is intelligible. Not only does the notion of defect no longer make sense, not only are biology and biological function impossible and anatomy made unintelligible, but even efficient causality is made unintelligible and science impossible, as the very fact that an effect follows from a cause, that is is not arbitrary, presupposes telos.)