David Brook's column in Monday's New York Times, ambitiously titled "The End of Philosophy", exhibits the kind of assumptions about ethical philosophy that one might expect from someone who possesses a passing acquaintance with the subject, and while philosophers should appreciate any press they receive these days (philosophy does not enjoy the same level of public awareness that it has for most of its existence), Brook's assumptions about philosophy misrepresent it in ways that ought to be corrected.
In the first paragraph, Brooks attributes to Socrates the belief that the way to treat moral issues philosophically can be formulated as follows: "Think through moral problems. Find a principle. Apply it." Even the slightest survey of Plato's corpus would reveal just how alien such a formula would be to Socrates; Plato does not represent Socrates as a systematic thinker at all, and his dialectical method does not involve reasoning towards universal, objective laws. We understand Socrates properly only if we think of him as a model of how to think philosophically, not by taking his statements as propositions one places within the Platonic or Socratic system; and when one does this, one fails to live up to Socrates' standards of philosophical thinking.
If we consider for a moment Aristotle (a more systematic thinker, and probably more representative of the Greek mind), we find that he actually declares that the postulation of universal moral laws violates the basic nature of ethical inquiry. Instead, he says, one ought to talk about what occurs most of the time in ordinary situations. Decency, for Aristotle, consists in the ability to tell when a rule or standard that usually applies ought not be enforced due to unusual circumstances. Neither does one find the purpose of his ethics inflexibly rational, for the ethical life simply is the happy life--happy in the full meaning of the term.
Brooks attributes to Socrates a more modern approach to ethics, which--probably unconsciously, for the most part--sees ethical inquiry as similar to the scientific enterprise. He finds, on the basis of the data, universal laws not bound to the particularity of concrete circumstances. If Brook's directs his characterization of moral philosophy to any actually existing philosophical tradition, it would probably be deontological ethics. But even assuming he is aware of duty based ethics as formulated by Immanuel Kant and others--which is probably a stretch--nothing Brooks puts forth constitutes an argument against it.
While I am no Kantian, the idea that the discovery of natural, psychological causes and historical/genetic origins of a "moral sense" in human beings somehow threatens Kant's ethics betrays an ignorance of even its rough outlines. Kant acknowledges that most of the time people "do the right thing" as a way of pursuing personal happiness grounded in animal impulses, and the news that the genetic causes of these "animal impulses" turned out to be in-group cooperation understood within a Darwinian framework would simply support his conviction about the general human condition. However, Kant maintains that the moral law governing the will demands not only that one's acts conform to the moral law, but that one's will itself be put in submission to the moral law; and this law consists in nothing else but that the will recognize its own rational demands on itself. The moral agent ought not simply "think through moral problems", but instead acts in a way consistent with the nature of moral action itself. How this gets worked out can be complicated; in order to fully understand it, one has to read The Groundwork for the Metaphysics of Morals, The Critique of Practical Reason, and Religion Within the Bounds of Reason Alone.
Even if David Brooks were not familiar with Kant's ethics, familiarity with Kant's metaphysics would have revealed that no inner-worldly cause could possibly determine the nature of morality in principle: good and evil do not show up in sensuous perception, and so they must be placed in the noumenal, rather than the phenomenal, sphere. Scientific observation, Kant claimed, can deal only with what falls within the phenomenal sphere; i.e., science deals with causes which can be observed and verified, rather than the structures of the experiencing subject. While one might be able to locate the origin of moral intuition within the natural world of causes and effects, it does not follow that moral intuition is actually correct; Kant makes the case that morality can be seen as what the will necessarily postulates in order to make any sort of decision at all, and he places the will itself in the noumenal, supersensual realm.
None of this establishes whether or not Kant should be considered correct in either his metaphysical or his ethical claims; but it should be clear that nothing Brooks says amounts to an argument against deontological ethics--not even a bad argument. That our feelings about right and wrong are tied to our nature as a living organism with a history would not be denied by any serious ethical philosopher, but it does not follow in any obvious way that our feelings about right and wrong are accurate, nor does it say anything about whether our moral sense reaches out towards a transcendent moral order. These questions are simply not scientific questions; they are philosophical questions. And rather than signifying the end of philosophy, Brooks unwittingly shows why philosophy is necessary.