The fifth and last of St. Thomas Aquinas’ Five Ways is the argument from design, or, as he calls it, the argument from the governance of the world. We’ve already talked about medieval people saw purpose and meaning in everything around them. Sometimes they were mistaken about the mechanics of how things happen in the natural world or in medicine, but they saw that the world is basically ordered and logical, and they were able to study the natural world and expand their knowledge and understanding. They were able to build amazing feats of engineering, like the Gothic Churches (Notre Dame Cathedral, Paris), even without our modern technology.
As our understanding of the natural world expands we find more and more of what seems to be design at every level of creation. Everything has an end, or purpose, that is logical and predictable once we understand it. In the natural world, every member of an ecosystem has an vital function, bacteria, insects, prey, and predators, and if you remove part of the ecosystem, like when they killed the last of the wolves in Yosemite National Park, or add in something that doesn’t belong, like introducing cane toads to Australia, can have catastrophic consequences.
We find design in subatomic particles in the number and arrangement of neutrons, electrons, and protons, and we find design in the structure of the universe itself, from the Big Bang to today, everything holds together. When something doesn’t hold together we don’t assume that it just is that way or that it’s just illogical; we assume that we haven’t yet found the explanation. For example, if you find a hut in the middle of the desert you wouldn’t assume that a tornado stacked up a bunch of rocks and wood and branches that way purely by chance, but that a person had built it. There is far more design in the universe than there is in even the grandest house. If, for example, the explosion of the Big Bang had been one trillionth of a degree hotter or colder then carbon could not have developed, and carbon is necessary for all known life. Also, if the force of gravity had been a fraction of a percent stronger or weaker the stars could not have formed. Out of trillions of possible universes, this is the one we got.
St. Thomas Aquinas puts it like this. We see that things which lack intelligence act for an end, so as to attain that end, as the stars and planets move in a certain way. They achieve that end by design, and not by chance. Something that lacks intelligence cannot act towards an end unless it is directed by something that has intelligence, such as an arrow shot by an archer which cannot reach the target on its own but must be directed. Therefore, some intelligence exists by whom all natural things are directed to their end, and this we call God.
The arrows flight can be explained by the laws of gravity, aerodynamics, etc., but it’s direction can only be explained by the person who directed it. The movement of planets, stars, and galaxies can be explained by the laws of physics, but it cannot explain the fact that it seems to be directed towards the development of human life.
St. Thomas Aquinas’ five ways probably won’t convince someone who has different assumptions about existence than Christians do, and they don’t even prove everything that the Bible teaches us about God. They do, however, describe an intelligent, necessary First Cause who is the source of all perfections. We can argue about whether they prove our faith, but they certainly help us to understand it a little bit better.
Fr. Bryan was pastor of Our Lady of Lourdes from July 3, 2017 to June 2022.