Why be moral?

     I heard an atheist calling in to a Catholic radio show this morning with the following point:  atheists are quite as capable as Christians are of leading moral lives, and it is quite possible for an atheist to be a “good person”, and many in fact are.  The hosts of the show answered the caller respectfully (as always) and thoughtfully, but they missed (atypically, let me hasten to add) a crucial point, the crucial point: no serious Catholic I know of is arguing that atheists cannot be moral; rather, that without the authority of God morality is purely subjective, a personal choice on the part of the atheist.  There is no objective reason why he should not be immoral, since there is no objective standard of right and wrong.
     It is true that non-Christians, including atheists, can embrace natural law, as I discussed in an earlier post [here].  Not only that, but, as the radio hosts pointed out, St. Paul tells us:

For it is not the hearers of the law who are righteous before God, but the doers of the law who will be justified.  When Gentiles who have not the law do by nature what the law requires, they are a law to themselves, even though they do not have the law. They show that what the law requires is written on their hearts, while their conscience also bears witness and their conflicting thoughts accuse or perhaps excuse them . . . (Romans 2:13-15) 

     The problem is that in our fallen state we have other influences, other “spirits” as St. Ignatius of Loyola would put it, who are urging us in other directions.  That is one reason why we need Divine Revelation.  As I argue in another place [full article here], the less Christian our society becomes, the stronger those other voices will become, and the less likely the atheistic or indifferent are to heed the law written on their hearts:

Our civilization has been shaped by Christianity for almost two thousand years.  Christian beliefs, attitudes and moral convictions (commonly referred to as the Judeo-Christian worldview) are woven into all of our customs and institutions.  It is true that we have never realized the Christian ideal; one could say that we haven’t even come close.  Nevertheless, anyone raised in the West over the last two millenia has been formed, to a large degree, by that Christocentric worldview, whether they consciously embrace it or not.  More than one commentator has remarked that even the “new atheists” such as Richard Dawkins and Christopher Hitchens have not jettisoned principles such as the dignity of the human person (not a universal value by any stretch) or a Judeo-Christian concept of justice — they employ these very ideas, in fact, as weapons against Christianity.  This is confirmed by my personal experience: most self-proclaimed atheists with whom I am personally acquainted still adhere to a mostly Christian ethical code (even though they can’t give an authoritative reason why), with the usual exceptions involving sexual morality — which doesn’t do much to distinguish them from most professed Christians.

Without its source and foundation of Christian belief, however, the worldview itself will quickly wither . . .

     That, I think, is the counter to the atheist’s challenge: it’s not that an atheist can’t be moral, but rather, without God, why should he?