I meant no more than the citation (in your words) afterward explains.
Here's a tidbit from Gilson in Being and Some Philosophers.
The world of Aristotle is there whole, in so far as reality is substance. It is the world of science, eternal, self-subsistent and such that no problem concerning existence needs nor can be asked about it. It is one and the same thing for a man in it to be "man," to be "one" and "to be." But while keeping whole the world of Aristotle, Thomas Aquinas realizes that such a world cannot possibly be "metaphysical." Quite the reverse, it is the straight "physical" world of natural science, in which "natures" necessarily entail their own existence . . . physics is that very order of substantial reality in which existence is taken for granted. As soon as existence no longer is taken for granted, metaphysics beings. In other words, Thomas Aquinas is here moving the whole body of metaphysics to an entirely new ground. In the philosophy of Aristotle, physics was in charge of dealing with all "natures," that is, with those beings that have in themselves the principle of their own change and of their own operations . . .But tell me, how could you be talking metaphysics when it concerned the the natural world?
As soon as existence no longer is taken for granted, metaphysics begins.
Because there's more to "the natural world" than physics, cornelis. Plus even the physicists and biologists can't seem to avoid doing it. As a case in point, much of modern day science is firmly premised in the philosophical doctrine of materialism. I've recently mentioned other examples hereabouts.
I mean, human beings are a part of nature; they are thus "natural." They also seemingly happen to be more than the sum total of the cells and molecules and the astronomical number atoms and sub-atomic particles and atomic quantum states that compose their bodies. It's not even possible to make a "full description" of a living organism or a human being based on the methods of present-day physics: Who knows, for example, how to gather and collate information about a virtually astronomical number of quantum states, affected by quantum events continuously triggered from "outside" the organism, which would also need to be quantified, which would be necessary for a full description of a living organism in physical terms?
The biologists have basically taken the position that life must be taken as an irreducible, foundational "given," and then just go on from there, happy as clams. To ask 'what life is?' is a foolish question from the standpoint of methodological naturalism: You do not have to know the answer to this question to do first-rate science. Similarly physicists take the quantum of action as irreducible to anything that could be further detected by science. Life and the action principle are both taken axiomatically.
I am fascinated by, and honor, the findings of state-of-the-art theoretical developments in the sciences. But to the extent that there's "more to man (and the world and society) than mere matter," neither physics nor biology has the complete answer to the questions that matter most to most thinking human beings -- and they are likely unable to produce one, on sheer methodological grounds.
So I admit I do see philosophy as fully "complementary" with the natural sciences. You don't get to do both at the same time, and possibly no one person can effectively do both equally well anyway; but you do need them both to make a "full description of the system" that includes living beings and especially man. :^)
Thank you so much for Gilson's statement RE: Aristotle's attitude toward his own philosophizing -- "In the philosophy of Aristotle, physics was in charge of dealing with all 'natures,' that is, with those beings that have in themselves the principle of their own change and of their own operations." Obviously, this attitude is founded on the premise that "nature" (or "natures") is to be defined as what bears within itself the principles of its own change and operations. Living beings, however, are finite and contingent; so it appears they cannot wholly be responsible for their dispositions themselves; they do not completely reduce to the expectation of the physicial sciences that once you know the initial conditions, then the laws of physics do all the rest.
Rather than the term "metaphysics" (incorrectly credited to Aristotle), I'd really prefer to use the more generic term, "philosophy" instead. Metaphysics has become identified with particular schools and doctrines; philosophy (as practiced by Plato and Aristotle) gives us a chance to return to "realist" models of exploring and understanding reality.
It seems the fundamental prejudice of a certain contemporary scientific attitude that no causes of things can arise outside the familiar four-dimensional space that we normally experience. And yet curiously I note that no "universal" seemingly can arise there either -- at least if you believe in the law of cause-and-effect as the lawful result of the actions of real bodies in close proximity on each other. Universals do not appear to be the products of four-dimensional spacetime "nature", but somehow as "ulterior" to it; but that nature appears to depend on and be governed by them. The physical laws of science themselves are universals.
Thank you so much for writing cornelis. Truly I value your comments. Obviously, I am still struggling to put my ideas into cogent order here, and to find adequate language to express them clearly.... It's good to have a highly well-qualified interlocutor.