Objection: Evolution shows that organs do not have an inherent purpose. We know that organs are the product of random mutation and natural selection – neither of which are directed toward some goal. Those with certain organs tended to be more conducive to survive than others and that’s all there is to it.
Response: Evolution doesn’t assign a purpose because it’s built not to look for purpose from the get-go. The goal of evolution has been to discover the efficient cause of life, not its teleology. If an organ like the heart was caused by random mutation and natural selection (R&N), this doesn’t entail that R&N can’t cause the heart to have the purpose of pumping blood through your circulatory system. For something to have a purpose, all that’s required is that it have a function or regular tendency toward a certain outcome. Under this definition purpose need not be driven by some conscious agent but can be completely unconscious.
Furthermore, if you study the origins of modern science (or study philosophy of science) you’ll discover that teleology was seen as a distraction, not that it was non-existent. Bacon and Co. thought science should have a this-worldly focus – meaning that we should be concerned with humanism and producing technology that will benefit us here and now. Science was consequently repurposed to understand “how” something works and not “why” it works. Not only was it repurposed, but it was reinterpreted in light of a mechanical view of reality.
Imagine this scenario: Suppose I wanted to create a crude calculator that would benefit me for mathematical calculations. I have in my possession an ancient artifact known as a hand watch. Now I don’t know what the hand watch was used FOR, but I don’t care because all I want to know is how it works in order to repurpose its mechanism as a calculator. This is exactly what happened with modern science. Scientists today are not concerned about a thing’s purpose. As Bacon, Galileo, and others would say, they just want to uncover natures’ secrets primarily for humanitarian benefits (medicine, exploration, technology, etc). So a thing’s purpose becomes an irrelevant consideration.
After teleology was pushed off the radar for so long, later thinkers came to believe that science proves the non-existence of teleology because it has done just fine without it and has never been discovered. But this is no better than someone claiming that a metal detector proves the non-existence of glass. Metal detectors aren’t made to discover glass in the first place, and even if glass didn’t exist, it would be absurd to argue for their non-existence through metal detectors. Similarly, modern science just isn’t made to discover teleology in the first place and even if teleology didn’t exist, it would be absurd to use science as an argument.