I've been reading Edward Feser's Aquinas; a Beginner's Guide, in the hope of understanding Thomist philosophy, and especially in understanding why Thomist philosophers such as Prof. Feser object to Intelligent Design Theory. I've read some of Feser's blog posts that are critical of Intelligent Design, but I think the crux of the problem can be found in the following passage from his book:
"Now machines, or at least complex machines, might seem to exhibit immanent causation of the sort definitive of life. We say, for example, that a coffee machine can turn itself on in the morning, that computers can run self-diagnostic routines, and so forth. So, could machines count as living things on Aquinas's view, and thus as having souls? They could not. For a living thing is a kind of substance, but machines are artifacts. And though an artifact can be described in a loose sense as if it were a kind of substance (as we did in chapter 2 when using examples like the rubber ball), in the strict sense an artifact is not a genuine substance at all, in Aquinas's view, but rather a composite of substances, or of parts of substances (In DA II.1.218; SCG IV 35.7). This is evident from the fact that the parts of an artifact have no inherent tendency to come together and function as a coffee machine, or computer, or whatever, but have to be arranged by us to do so." (p.136-137)
Living cells have very important parts: proteins, RNA, and DNA. The problem is that many or most ID hypotheses would say that the parts
of living things have no inherent tendency to come together and
function, just as the parts of machines have no inherent tendency to come together and function.
Proteins are made of "left-handed" amino acids, that are put together in very specific order. There is no inherent tendency for amino acids to separate the right-handed amino acids from the left-handed amino acids. And there is no inherent tendency for the amino acids to come together in the very specific order that are required for them to function properly.
Meanwhile, RNA and DNA are made of "right-handed" nucleotides, that are also put together in a very specific order. There is no inherent tendency for nucleotides to form in the wild. There is no inherent tendency for them to separate the right-handed nucleotides from the left-handed nucleotides. There is no inherent tendency for them to come together in the very specific order that are required for them to function properly.
Once there is a living cell with all the proper parts in the proper order, then they can function properly and make more proteins, RNA, and DNA, and do all the other things that living cells do. But until there is a living cell there appears to be no way to get one without somebody putting all the proper parts together in the proper way.
And thus, at least the first living cell seems to have resembled a machine: somebody had to arrange its parts before it could function.
Now most (but not all) ID theorists think that much of evolution could only take place with the aid of somebody doing a lot more arranging of parts. So if these ID theorists are correct, at least some of the new living organisms that evolved also resembled machines.
Thus, it seems that if ID is true (or at least the forms of ID that require this type of "tinkering"), then this would be a challenge to the Thomistic understanding of what living organisms are.
Perhaps there is a solution: Perhaps God has created the universe so that the right kind of parts, once they are arranged in the proper way, become a living organism. Thus, the right kind of parts do not have an inherent tendency to "come together" by themselves. But once they have come together, they do have an inherent tendency to function as a living organism.
I don't know if Prof. Feser or other Thomists would consider this a real solution. Perhaps not. But if not, then I think at least this part of Thomism is false. Empirically false.