(Continued from "Aquinas on Causality: Any Recommendations?")
I'm particualry interested in formal causation as I'm discussing the soul and the non-life to life problem with a few materialists who dont think formal causation exists.
Ok, I see! So you're interested in formal (and material) causality as it relates to philosophical psychology. Then I'd say:
1) Fr. H. D. Gardeil's volume on Psychology (vol. 3), chapter 1-3, especially 2. There he provides a critique of "mechanism" too, which is a version of materialism.
2) D.Q. McInerny's book on Philosophical Psychology should be helpful if you don't have access to Gardeil.
3) Aquinas, "Commentary on Aristotle's De Anima," Book I, Ch. 5, contains the fundamental treatise on this issue.
4) Aquinas, ST I.75-76, especially 75.1. This is the solution to your problem in a nutshell.
5) Robert Pasnau, "Thomas Aquinas on Human Nature," chs. 1-3, especially 3.
Pasnau is by no means a traditional Thomist (he's way too avant-garde for me) but he has an interesting approach that might help you refute materialism in a convincing way.
But instead of just giving you references, I'd also like to lead you in the right direction, philosophically.
The crux of the problem is: Bare matter, by itself, is chaotic, mere stuff. The living matter within an organism is not bare, crude matter. It operates in a unified way, organically. So living matter is bare matter plus organic unity. And bare matter cannot cause itself to have organic unity--otherwise everything would be alive--so there must be something which gives it organic unity. What could be giving it its unity? What is this "principle of organic unification" (POU)? If the materialists are right, then the POU is itself material--because for them everything is material. But if the POU is itself made out of matter, then it must be asked: what provides organic unification for the matter out of which the POU is made? If you posit another material POU then you'll eventually run into an infinite and pointless regress. So ultimately we must posit a POU which is not itself dependent on another POU, that is, one which is not material. This is what we call "anima" as in "animating principle." (Some people call it "soul," but by this we need not understand some ghostly floaty thing that lives "caged" inside the body. Rather, the "anima" is simply the "first POU.")
This is basically the argument in ST I.75.1, where he concludes that "the soul is not a body", i.e., the soul is not a material POU, but an immaterial one.