[I am happy with the themes in this post, but the arrangement and logical flow seems a bit wonky, so I may shuffle, expand, or disembowel things in it over the next few days.]
Behind every question lies an assertion. This is not the case for rhetorical questions only. Any question, precisely by being raised, carries with it a host of premises, or tacit assertions, such as the mutual coherence of spoken language (á la the gavagai problem), the existence and proper function of other minds outside one's own mind, the persistence of audible meaning through changing spacetime, the benefit of gaining such knowledge, the reliability and authority of the person being queried, the intelligibility of the world as something that can be understood in the first place, and so forth. Some questions are asked to narrow the rang of implicit goals––"Where are my keys?"––, while others are designed to broaden the scope of possible answers––"Was yours a happy childhood?" I want to consider one question in the following that I think implies a great deal about the scope of morality and truth.
Question: Are humans anthropocentric?
Prima facie, the question seems to answer itself: Of course they are! Of course it seems rational to call anthropoids anthropocentric, a case when the prima facie reading is res ipsa loquitur. But this reflex is wrong. The question is not asking whether humans are anthropic, but anthropocentric.
Consider two similar questions: 1) Are cars automotive? 2) Are cars 'automotocentric'? The difference between these questions should be clear, and when applied to humans, very illuminating. Are humans anthropocentric? No more than cars are automotocentric.
Indeed, to be an automobile is to 'be there' for something outside of and greater than the car itself. To be 'automotive', then, is to be non-automotocentric, precisely because being automotive means being anthropocentric. Because a car is radically open to its 'being there' for the benefit of others, we drivers, it becomes difficult to see a car as even a fully automotive entity. Its automotocentricity, in other words, compromises even its more basic automotiveness. Some of the ways in which a car loses its automotcentricity negate certain of its automotive features. If a car were just sitting in a parking lot, it would be fully automotive; it would be "doing" what a car does in and of itself. But once its apparent automotocentricity were dispelled by the entry of a human driver, the car's structure would radically change. What were formally mere car parts welded together, suddenly become anthropic tools. The human agency behind the wheel not only explodes the illusion of a car 'being there' for itself (viz., automotocentricity), but also denatures, as it were, the car's otherwise intact automotiveness. Its many parts cease to be automotive and become anthropocentrized. Despite the fact that a car is needed for all of them, it is foolish to see actions like signaling, honking, braking, accelerating, turning, idling, and parking as automotive operations. All such actions are only materially automotive; formally, they are human actions performed by way of a car. The fact that we can perform the same actions, albeit in non-automotive ways, without a car, indicates their fundamentally human, and only derivatively automotive, nature.
So it is with humans. To be a human is to 'be there' for something actually there, something which we do not create from within ourselves, but whose existence, or, dynamic presence, actually forms the field in which we exist as ourselves. There is no 'I' without a 'Thou', and, as Levinas has expressed so well, there is no 'I-Thou' without a surrounding 'We'. By extension, to climb that infamous ladder of Being, to be human is to exist by virtue of the grace of God, whose dynamic presence in every nook and cranny of existence keeps us floating along, as it were, on the river of space and time. We can only exist by going out from ourselves, or, by being 'anthropoperimetric' or 'anthropocircumferential' (the perimeter/circumference being the opposite of the center). If humans are strictly anthropocentric, humans are not. I am convinced the same stricture against strict anthropocentrism holds for humanity as a whole. The entire point of there being a human nature is that humanity is present, somehow both in fieri and in whole, in each human person. As has been said (cf. Jerusalem Talmud, Sanhedrin 4:8 (37a)), to kill one life is to kill the human race, and to save one life is to save the whole human race.
What I have said to up this point may seem too grand, or too jesuitical, since it may seem obvious that the thrust of the question––Are humans anthropocentric?––is not asking about the existential and phenomenological bases of human experience, but rather is asking a basic question about human life at large. The question is asking whether the whole tumbling human adventure is simply humanistic, or if there is "more to it" than that. Is morality, for example, a strictly human matter, as Einstein held, or is it something more than human? Is man the measure of all things? So far from my comments about I-Thou, etc. cutting against anthropocentrism, a humanist would be wise to agree that our consciousness and cognition requires other human beings––and count it as proof of the inescapably human, anthropocentric nature of the world as we know it.
I demur, however, that the issues of intersubjectivity, openness to objective reality, and the like can be so easily subverted to humanist ends. I am not a humanist because I believe everything about human existence points beyond its strictly humanoid dimensions, just as a car in use, fulfilling its "purpose" points beyond its sheer automotiveness. Human life, in other words, is a vehicle for something greater that not only explodes the illusion of anthropocentricity, but also sublimates our very humanness from within based on a higher agency. The many actions each of us performs every day, are, like those of a car, not intrinsically individual (just as a car's actions are not intrinsically automotive). Our very openness to others, both mortal and immortal, renders even our simplest actions into egoperimetric, otherward, Godward performances. By extension, the many actions humanity performs, and the values it pursues, are not intrinsically anthropocentric; their very openness to reality at large (inorganic, organic, and divine) renders them anthropoperimetric, both subhuman-ward and superhuman-ward, as it were. The life of humanity, like the life of a car in traffic, is not only not anthropocentric (otherwise it is inert and useless, like an empty car in a parking lot), but also not even properly anthropic. Just as the actions of a driven car are formally, really, human actions by means of a car, so human actions at large are formally divine actions which bring humanity closer to its destination. Is a car the measure of all things for the life of cars? Not at all. A good measure of what cars can do, and all of what they pursue, is derived from the dimensions and goals of the driver.
The reason humans can operate cars as well as we do (or perhaps not!), is because they were designed around our bodies and faculties. To put it differently, the reason cars seem so 'docile' (i.e., teachable) when we are in them, is because they are designed to transcend their sheer automotiveness and be sublimated into human quasi-agents. Likewise, humanity's ability to serve as a vessel for divinity is based on the fact that the blueprints of our nature are, mysteriously, built around the theandric phenomenon of Jesus Christ as a free, existence-ratifying event. Christ, the God-Man, is the ideal coupling that links the superior agency of God with the inferior responsiveness of human nature. Man is ineradicably religious in the same way a car is magically and ineradicably drivable: we are designed to fit and function around a superior agency within. All our values, therefore, are no more a strictly human affair than the features of a fully loaded car are strictly the concerns of the car. To say otherwise, to say that human concerns are purely human, wold be as foolish as saying that my concerns are purely my own. The impossibility of having values, ethics, and knowledge apart from your social peers and larger tradition, is just an analogy for the nonsense of proposing purely human values, ethics, and knowledge apart from the triune immanence of God and the tradition of Divine Revelation.
This is not merely a social matter, either. Humans by nature reach out sensibly to experience and influence the world. It has been said the smallness of humankind can be seen by the fact that we can imagine the world without us in it. So it is. As a Catholic I am all for demolishing the insular illusions of human autonomy. What is at issue, however, is not the smallness of humans, but the literal 'eccentricity' of human nature. We are irresistibly drawn outward, and it is this that guarantees we are voracious knowers. We may be able to imagine the world without us in it, but, crucially, we cannot imagine ourselves without the world. Our givenness, as if it were some kind of ethical or philosophical license for autonomy, is thus dependent on that to which we are given. This is all tied in with the classical view of man as a microcosmic mediator between the subhuman and the superhuman, mindless matter and Mind. Mankind, then, is no more coherently construed as the measure of all things than a man is taken to be the measure of himself when he says, "I know how tall I am," and places his hand atop his head to prove it, a tautology in action. Of course a man is as tall as he is; but we still must ask, how tall is he? The point of the analogy is that a measure, a standard, must be separate from the thing being measured. Quite so. Which is why the standards by which a man, and all people, are assessed must be separate, though not removed, from the nature of man himself. Humanism insists people are the measure of all things––and pats itself on the head to prove it, now a collective tautology in action. It is a tautology to say that everything humans discuss and value is everything humans discuss and value, but this tautology is all that humanism amounts to: an illusion that because we are oriented toward this and that end (e.g., beauty, God), or because we feel this or that sensation (e.g., hot, cold), then there is nothing more to this and that.
At every point a car is doing what the car is doing, but this tautology on wheels in no way means a car is doing only and entirely what a car does, or can do. A car can do more than a car can do by nature (in the parking lot), even though it does that "more" naturally in a carlike way. In fact, the car-ness of a car's human behavior only reinforces the magical link between the car's 'being there' for its driver and its yet unviolated nature as a car in the service of the driver. A car being driven can be more than a car, yet without ever being forced to less than a car. Likewise, we humans can still be human by 'being there' for God, and do so naturally without being any less than human, but we can't sensibly say the only things there are what we find ourselves doing.
Luther was fond of calling fallen man homo incurvatus in se ('man curved in on himself'), and I think the same depravity extends to our cognitive careers. If each human were cognitively curved inward (a problem known technically as omphaloskepsis!), he would never know anything but himself, and since the very concepts of self, body, motion, change, etc. are derived from a dynamic interaction with the world, knowing himself would mean knowing virtually nothing at all. By extension, if the body human confined its cognitive interests and certainty to its own collective navel, we would be just as ignorant to the larger, normative field of reality that is the basis for our coherence as one species among species. Humans, again, are not anthropocentric, but cosmocentric. If we were anthropocentric by nature, we would be drawn to things anthropic; but, strangely, we are drawn to a vast, unblinking, barren, voiceless cosmos. Because I believe the world, in turn, is not cosmocentric, but theocentric, on account of its radical contingency, I believe our cosmocentricity is just a prolegomenon to our properly theo-, nay, Christocentric existence. We are, individually, contingent upon others and our little worlds in the same way humankind, collectively, is contingent on the Ultimate Other and the eternal World of His Truth. We find our-selves in others, others in the world, and the world in the Mind of God. Humanism––methodical anthropocentrism––is, to put it bluntly, is a case of collective egocentrism. We find our center in the Mass, in the living convergence of two cross beams, in the pure act of giving and being-given, in the name of the Father, the Son, and the Holy Spirit.
 I place this word in inverted commas to indicate its Heideggerian vintage. For Heidegger, Dasein is the complete mode of active human existence in the world, literally, There-Being.
 A related consideration is the Scholastic distinction between actus humanus and actus hominis. An actus humanus is an 'act of a man', an action motivated by conscious free will. See here for much more detail [PDF]. An actus hominis, by contrast, is an 'act of man', a general action generated by natural reflexes and non-rational behavior. A man honking and swerving off the road to avoid a child comprise an actus humanus, whereas that same man rolling down the hill, screaming, and then dying, comprises an actus hominis. For the purposes of this essay it might be well to differentiate [if only my Latin were any good!] between an actus vehiculus (a vehicular action) and an actus per facultatem (an action by means of…).
 Notice how we speak of cars "acting up" and "giving us trouble", almost as if mechanical problems were personal problems. An unused car never "acts up", for the simple reason that, stuck in sheer automotiveness, the car cannot act.
 I borrow this analogy from Wittgenstein, even if I employ for purposes he might not recognize or respect.