Peter Kreeft — Handbook of Christian Apologetics page 5
5. The Design Argument
This sort of argument is of wide and perennial appeal. Almost everyone admits that reflection on the order and beauty of nature touches something very deep within us. But are the order and beauty of the product of intelligent design and conscious purpose? For theists the answer is yes. Arguments for design are attempts to vindicate this answer; to show why it is the most reasonable one to give. They have been formulated in ways as richly varied as the experience in which they are rooted. The following displays the core or central insight.
1. The universe displays a staggering amount of intelligibility, both within the things we observe and in the way these things relate to others outside themselves. That is to say the way they exist and coexist display an intricately beautiful order and regularity that can fill even the most casual observer with wonder. It is the norm in nature for many different beings to work together to produce the same valuable end—for example, the organs in the body work for our life and health. (See also argument 8.)
2. Either this intelligible order is the product of chance or of intelligent design.
3. Not chance.
4. Therefore the universe is the product of intelligent design.
5. Design comes only from a mind, a designer.
This is not the teleological argument, this is closer to the modern arguments in support of ID. In these arguments, the concept of design is unclear and does not apply with any metaphysical certainty. It fails to demonstrate the existence of the God of classical theism with the same metaphysical force that the 5 ways display. In fact, it displays no metaphysical force at all, since ID claims to be scientific in the modern sense, meaning empirically verifiable. If you cannot see the distinction between these two types of arguments, one largely classical and the other modern, then you simply cannot claim to understand what either Aristotle or Aquinas is actually saying.
I am not being antagonistic for the sake of argument. I am saying that the weaknesses in the modern arguments from design are real and ultimately they will fail because they 1) cannot demonstrate with certainty the existence of the God of classical theism and 2) they accept the modern, meaning since Descartes, conception of nature which denies both final and formal causality, the first of which is central to the teleological argument for God’s existence. There is indeed some honor in attempting to show that the world just looks like it was designed intelligently, but the weight of this argument, I would say, has always been rhetorically powerful while being philosophically lacking.
P.S. Kreeft is probably well aware that Aquinas is not simply a forerunner of William Paley and thus knows that the ancient and medieval arguments for the existence of God are strikingly dissimilar in many key respects, but he also writes popularly for a largely modern audience, and I say this as someone who very much enjoys his books and lectures.