If you want to use a Catholic argument from design, please, use Saint Thomas Aquinas’: “We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result” (STh I, q. 2, a. 3). Note that nature acts “nearly always in the same;” so there may be variations. Also note that nature acts “so as to obtain the best result;” so there is natural selection.
Natural selection does not have any idea about what is the best result. It does not know what is best or worst. If we were reduced to the Darwinian worldview there would be no best or worst, but only temporary survival and death.
But more importantly, we might use St. Thomas’ argument for design in his Summa Theologica (On the Government of Things in General (q 103, article 1) where he argues against the claim that the world developed by chance (that is, Darwinian theory):
Certain ancient philosophers denied the government of the world, saying that all things happened by chance. But such an opinion can be refuted as impossible in two ways.
First, by observation of things themselves: for we observe that in nature things happen always or nearly always for the best; which would not be the case unless some sort of providence directed nature towards good as an end; which is to govern. Wherefore the unfailing order we observe in things is a sign of their being governed;** for instance, if we enter a well-ordered house we gather therefrom the intention of him that put it in order**, as Tullius says (De Nat. Deorum ii), quoting Aristotle [Cleanthes].
Or we could use the argument from Fr. James McWilliams, S.J. in his Catholic college textbook Cosmology:
Structural Order. Teleology is order in activity, and is therefore called dynamic order. But
there is also the order of structure. Structural order ; is the harmonious arrangement of diverse integral parts in one pattern or configuration. Thus the frond of a fern or palm has leaflets or blades, arranged along the stern in a recognizable pattern. Structural order is characterized by symmetry and proportion. Symmetry is the repetition of some feature, as in the similarity of two leaflets on opposite sides of the stem, or the two eyes of an animal. Proportion is the gradation of a feature or character according to a more or less fixed ratio; thus in the frond the row of leaflets on either side of the stem is arranged in gradually diminishing sizes from the base to the tip. Structural order is observable in the wings of a bird, in a snowflake, in a frost- flower on a window-pane. In fact, a most interesting study is the examination of natural objects, even with a microscope, to discover their intricate and amazing structures. Moreover, X-rays disclose a structure in the very atoms themselves.
It is true that structure is often suitable for useful activity, still it can be recognized without our knowing its utility. Hence, structural order, apart from dynamic order, furnishes
independent evidence for intelligence.
Or we could try the Thomistic Catholic philosopher Dr. Peter Kreeft:
The Catholic philosopher, Dr. Peter Kreeft gives a nice explanation:
Peter Kreeft — Handbook of Christian Apologetics page 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.
- 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.)
- Either this intelligible order is the product of chance or of intelligent design.
- Not chance.
- Therefore the universe is the product of intelligent design.
- Design comes only from a mind, a designer.
Or we could try the Catholic Physicist Stephen Barr’s book Modern Physics and Ancient Faith where he cites the Latin Christian writer Minucius Felix near the beginning of the third century:
”If upon entering some home you saw that everything there was well-tended, neat, and decorative, you would believe that some master was in charge of it, and that he himself was superior to those good things. So too in the home of this world, when you see providence, order, and law in the heavens and on earth, believe there is a Lord and Author of the universe, more beautiful than the stars themselves and the various parts of the whole world.”
I can provide a dozen more like this also, if interested.