The answer, in short, is that recognizing the centrality of man is far from outdated and cannot be branded as mere “anthropocentrism.” Man is qualitatively different from and, in fact, superior to all other material creatures, and this fact can be shown by a relatively easy philosophical reflection.
(I will preface my answer by saying that I understood the O.P. as taking “anthropocentrism” to mean that man has the central place among his fellow material creatures, not that he is superior to the angels or to God.)
The different degrees of action among material creatures
The easiest way to show this is to look at what different creatures are capable of. (It is important to note at this point that the analysis here is a philosophical one, not a biological one: we are not looking at how living things relate according to ancestry and genealogy, but simply what sorts of actions they can realize.)
As we observe material creatures, then, it soon becomes evident that there is a fairly sharp divide between living and nonliving beings. (Yes, there are a few cases that seem to straddle the border—viruses, prions, and so forth—but they are practically all parasites that take advantage of the replication apparatus of living things.) The fundamental difference, if one analyzes it, is that living things have an immanent principle of change, whereas nonliving things, as such, can only be changed by something extrinsic to them. On the contrary, living things can grow and reproduce, instigated from within (even though they certainly do interact with their environment).
However, things “live” to differing degrees, so to speak. All living, material things grow and reproduce; but some of them, it seems, do little else (plants, fungi, most unicellular life forms, and so on), whereas others are capable of sensation and movement (animals).
Even among animals, it is clear that the so-called “higher” animals have much more developed sensation and interior faculties (memory, imagination, and so forth) than the “lower” ones.
In short, all animals (and any other creatures—should they be found—that exhibit sensation) are simply capable of more than non-sensitive creatures; and all living things are capable of more than nonliving things.
(Again, the differing degrees of action do not necessarily follow evolutionary lines. For instance, some mollusks, such as octopuses, would probably be characterized as more “intelligent” than some mammals.)
One animal, however, shows unique and remarkable capabilities that are simply absent in all the others. Non-human animals are capable of a certain sensitive knowledge of their environment—they “know” things to the degree that it interests them and helps them obtain sensual satisfaction—however, they are completely incapable of universal knowledge.
(And yes, that includes the higher apes: chimpanzees and gorillas, in fact, have a remarkably well developed imagination and memory—in some ways, even sharper than ours—but none of them demonstrate the slightest ability to know what something is. They are adept at learning how things affect them—which is how they learn to make basic tools—but a chimpanzee cannot, for instance, describe to another chimpanzee what a tool is and how to make one.)
Man, unlike all the other material creatures, is capable of a kind of knowledge that is immaterial—which is the necessary condition for it to be truly universal.
Aristotle famously defined man as the “rational animal” for this reason: man has all of the capabilities of other living creatures (growth, reproduction, sensitive knowledge and movement) and in addition the ability to know things in a properly intellectual way. (See, for instance, Nicomachean Ethics, I.13, 1102a28. Aristotle by defining man like this does not mean to denigrate the so-called “lower” faculties; he is merely affirming that man has something more than those.)
In a similar way—and thanks to his intellectual faculty—man is capable of free action, in a way that animals simply are not. Give food to a non-human animal (even to a chimpanzee!), and it will eat, unless a contrary sensation impedes it (e.g., it is full). The animal has no choice in the matter. Man, on the contrary, can govern his actions, even his “lower” appetites (albeit not completely). For example, a man might refrain from eating food that he knows is poisonous or unhealthy; a non-human animal has no say in this matter.
The hierarchy of beings
Since different kinds of creatures display differing degrees of capability, it follows that there is, underlying that difference, also a diversity in nobility or intrinsic dignity.
A stone is a less noble creature than a tree, which is less noble than an insect, which is less noble than a giraffe, which is less noble than a man. Material creation, therefore, displays a hierarchy of being, in which some species are ontologically superior to others.
It should be noted at once that this hierarchy applies among diverse species, never within a given species. In particular, all human beings have the same fundamental dignity, thanks to their rational (and, as we will see, spiritual) nature.
(Regarding the hierarchy of beings, see Summa theologiae, I, q. 47, a. 2, especially the responsum. Regarding the faculties of the soul, see I. qq. 78-81.)
How man is different from all the rest: man as a spiritual creature
We are now in a position to see what makes man different from all the rest of the material creatures.
Although there is a hierarchy across all of creation, it should be observed that the first three levels—non-living, living but not sensitive, and sensitive—can all be reached by beings that are entirely material in their constitution.
Even the most noble of the activities we noted—sensitive knowledge—is reachable using sense organs and a brain: complex, but still material, things.
On the other hand, rational knowledge—which consists in universal knowledge of things and acknowledgment of their existence (or non-existence) in reality—cannot be reduced to the operation of material organs. It is not my brain that tells me “a giraffe is a mammal that looks something like a horse with a very long neck” and “there are giraffes in the wild in Africa.” I have never seen a giraffe in person—but I know what one is and would recognize one if I saw it. Hence, that knowledge must be in something that is beyond the brain, something immaterial: my intellect.
If man has an immaterial faculty (actually, at least two immaterial faculties, because, in addition to his intellect, he has a will, which gives him freedom of action, as I mentioned above), it follows that man is immaterial by nature (in addition to being corporeal, as is evident).
And being immaterial by nature is precisely what is meant by the term spiritual.
Hence, man—in contrast to all other material creatures, even the highest—is a spirit, a creature that—although fully “incarnate” in a body—is not limited by his materiality.
Hence, the divide between rational creature and non-rational is far greater even than the divide between living and nonliving. Therefore, for example, the life of even one human being is worth the life of all non-human beings combined. (This does not, of course, authorize us to go on a rampage against such living things, but it illustrates the infinitely greater dignity of a human being over a non-human being.)
“Anthropocentrism” is in accord with good sense and hence, also Christianity
In conclusion, man, unique among all creatures, is a rational, and hence a spritual being (a being not limited to his materiality). It follows that the dignity of even one man is incommensurable to the dignity of all the non-human material creatures. Such creatures, therefore, are at the service of man and must be used accordingly.
(It is absolutely true that the environment, for example, must be taken care of. However, the fundamental reason for this is that it must serve man properly, which it will not do if it is polluted or otherwise compromised.)
It entirely reasonable, therefore, for Christianity to be “anthropocentric.” Only man (among material creatures) is spiritual, hence only man can sin, and hence only man can be saved. (Animals can be said to have souls—souls, in the Aristotelian tradition, are the so-called “substantial forms” of living things—but their souls, which are not immaterial, do not survive death. Man’s, yes.)
If we add to this the fact that the Divine Son became incarnate as a man, then we see that the entire human race is the subject of divine predilection—in a way other, sub-human creatures are simply incapable of.
A few more reflections
I will observe that any pretense to avoid “anthropocentrism” can rather easily be shown to defeat its own purpose.
We must not—a non-anthropocentrist would argue—value man above other creatures. That is interesting, but in that case, it is strange that man seems to be the only creature capable of taking care of the others. If chimpanzees and gorillas had rights on par with human beings, we would expect them to form unions and constituencies to defend those rights—but they evidently are not capable of that sort of thing.
Rather, it is irremediably the task of man to take care of the environment, or to prevent its destruction.
This fact is evidence of man’s intrinsic superiority: only man is a rational creature, hence only he can understand what “species,” the “environment” and “taking care of them” are, and only he actually has the freedom to take care of them.