"Sex Codes Among Inner-City Youth" is the title of a remarkable paper presented this week by University of Pennsylvania Professor Elijah Anderson to a seminar at the American Enterprise Institute. Its 40 pages describe in excruciating detail the sex and abandonment "game" played by boys and girls in an inner-city Philadelphia community, one of the poorest and most blighted in the country.

Anderson is a scrupulous and sympathetic student of inner-city life. "Streetwise," his book on life in a ghetto community, is a classic of urban ethnography. Five years of intensive observation and interviews have gone into the sex code study. It is the story, as told by the participants, of family breakdown on an unprecedented scale.

It is the story of a place where "casual sex with as many women as possible, impregnating one or more, and getting them to 'have your baby' brings a boy the ultimate in esteem from his peers and makes him a man." As for the girl, "her dream {is} of a family and a home." But in a subculture where for the boy "to own up to a pregnancy is to go against the peer-group ethic of 'hit and run,' " abandonment is the norm.

The results we know. Illegitimacy rates of 70, 80 percent. Intergenerational poverty. Social breakdown.

Toward the end of the seminar, I suggested that the only realistic way to attack this cycle of illegitimacy and its associated pathologies is by cutting off the oxygen that sustains the system: Stop the welfare checks. The check, generated by the first illegitimate birth, says that government will play the role of father and provider. It sustains a deranged social structure of children having children and raising them alone and abandoned by their men. To quote Anderson: "In cold economic terms, a baby can be an asset, which is without doubt an important factor behind exploitative sex and out-of-wedlock babies."

It is a mark of how far the debate on welfare policy has come that my proposal drew respectful disagreement from only about half of the panel -- including, I should stress, Prof. Anderson himself, who argued that the better answer is giving the young men jobs and hope through training and education for a changing economy.

In fact, the idea I proposed is not at all original. I was merely echoing Charles Murray, who in his book, "Losing Ground," offered the cold turkey approach as a "thought experiment." That was a decade ago. Two weeks ago in the Wall Street Journal, the national illegitimacy numbers having become dramatically worse, Murray dropped the "experiment" part and proposed it as policy.

Nor is this idea coming only from conservatives. Neo-liberal journalist Mickey Kaus proposed a similar idea in his book, "The End of Equality," though in a less Draconian variant: He would replace AFDC and all other cash-like welfare programs with an offer of a neo-WPA jobs program.

And last year, candidate and "New Democrat" Bill Clinton gingerly approached the idea with his two-years-and-out welfare reform plan. But "two years and out," however well intentioned, misses the point. The point is to root out at its origin the most perverse government incentive program of all: the subsidy for illegitimacy.

Why? Because illegitimacy is the royal road to poverty and all its attendant pathologies. As the 1991 Rockefeller Commission on Children acknowledged, the one-parent family is six times more likely to be poor than the two-parent family.

The numbers simply translate common sense. In a competitive economy and corrupting culture, it is hard enough to raise a child with two parents. To succeed with only one requires heroism on the part of the young mother. Heroism is not impossible. But no society can expect it as the norm. And any society that does is inviting social catastrophe of the kind now on view in the inner cities of America.

The defenders of welfare will tell you that young women do not have babies just to get the check. Yes, there are other reasons: a desire for someone to love, a wish to declare one's independence, a way to secure the love of these elusive young males and a variety of other illusions.

But whether or not the welfare check is the conscious reason, it plays a far more critical role. As Kaus indicated at the seminar, the check is the condition that allows people to act on all the other reasons. Take it away, and the society built on babies having babies cannot sustain itself.

Taking it away is the single most immediate and direct measure that government can take to break the cycle of illegitimacy and dependency. Moreover, society will not long sustain such a system. Americans feel a civic obligation to help the unfortunate. There is no great protest when their tax dollars go for hurricane relief or for widows and orphans. But by what moral logic should a taxpayer be asked to give a part of his earnings to sustain a child fathered by a young man who disappears, leaving mother and child a ward of the state? Underwriting tragedy is one thing. Underwriting wantonness is quite another.

On Oct. 19, Sen. Daniel Patrick Moynihan held a Finance Committee hearing on "social behavior and health care costs." What he really meant by social behavior was illegitimacy. In his opening statement, he drew attention to the explosion of illegitimacy in the general population. It has now reached about 30 percent of all births, 5.5 times what it was 30 years ago. It is a tragedy for the people involved, a calamity for society at large. "Now then," asked Moynihan, "what are we going to do?"

Try this. Don't reform welfare. Don't reinvent it. When it comes to illegitimacy, abolish it.