that amount every year—forever. Moreover, to bring the island’srnpopulation down to its carrying capacity Castro wouldrnhave to send more than 120,000 per year. In which case, asrnthe less crowded islanders became more comfortable, theyrnwould no doubt practice contraception less conscientiously,rnthus allowing fertility to rise and producing even more candidatesrnfor emigration.rnThen, as other overpopulated nations—overpopulated inrnthe judgment of their own people—became aware of thernprecedent set by the Cuban boatlifts, they too would dumprntheir surplus populations in Uncle Sam’s lap. It took less thanrna month for President Carter to realize the insanity of actingrnon what appeared to be Christian ethics. The President thenrnlet it be known that the Mariel boatlift was a one-time thing.rnThus did he, in effect, warn the 10 million people of Cuba,rnthe 6 million people of Haiti, the 5 million people of the DominicanrnRepublic, the 5 million people of El Salvador, the 7rnmillion people of Guatemala—and hundreds of other millionsrn—that they should not expect the United States to dismantlernits borders just because their people are in need.rn(These are the figures for 1980; since then the populations ofrnthese countries have increased by 24 percent, while the populationrnof the United States has grown by only 15 percent.)rnI would argue that the acceptance of unlimited numbers ofrnimmigrants only appears to accord with Christian principles.rnIs this where you and I have a difference of opinion? Let mernstate my position, and you can tell me where I’m wrong.rnIapproach immigration problems from the scientific side.rnAs modern science emerged in the 17th century, Galileornsaid that “the grand book of the universe is written in thernlanguage of mathematics.” Believe me, this is a central dogmarnin the faith of all scientists. Time after time a difficult questionrnthat does not obviously involve mathematics yields itsrnsecret once mathematical reasoning is introduced. Such successesrnlead some of us—I’m one—to believe that the disciplinernof ethics can also benefit from mathematical insights.rnWe must pay attention to quantities—the “q” of our “p’s andrnq’s.” I think there are many instances in which dealing quantitiesrninto the game—even in a rough way—permits us tornreinterpret traditional ethics in a manner suitable to practicalrnmen faced with practical problems.rnWhen Cain asked the Lord “Am I my brother’s keeper?” hernwas obviously thinking of only one brother, Abel (whom hernhad just liquidated). I don’t know anything about Hebrew,rnbut in English the very printing of the question confines thernconclusions to the singular case—”brother’s.” To go from thernsingular to the plural case, in English, you have to write “s”rnapostrophe, i.e., “my brothers’ keeper.” As far as ethics is concerned,rnperhaps the difference between one brother and twornwould not be enough to bother about. But suppose there arerna million brothers. Ten million. In all realism, must I be “myrnbrothers’ keeper” when there are hundreds of millions ofrnbrothers out there crying to be cared for? Quantities matter.rnWhat we call the “poverty line” in annual income is an arbitraryrnfigure, but by any evaluation reasonable to Americans,rntwo billion people throughout the world live below the povertyrnline. (Or maybe they only exist at that low level.) Therntrouble with large numbers like a million or a billion is that thernhuman mind does not easily grasp their implications. Wernneed to find a simple way to reduce large numbers—and largernobligations—to the human scale. In the present instance.rnthat’s easily done.rnA population of two billion wretchedly poor in the world isrnroughly eight times as great as the total population of thernUnited States. To get a feeling for the load this would create,rnlet’s imagine that the problem is handled at the family level.rnDinah, you come from a family of four—pretty typical forrnour country. If our 250 million people took in two billionrnimmigrants, that would mean each family’s share would be 32rnimmigrant-guests to be invited into its home. Of course wernwouldn’t do it that way: instead we would pay taxes to achievernthe same end. But I assure you that the total burden wouldrnnot be lessened by using taxation to deal with it. Whether inrnour homes or outside them, we would have to house, feed,rnclothe, educate, and find jobs for two billion immigrants.rnAnd if the guests maintained the fertile habits of their homelandrn(as they undoubtedly would), the next year each Americanrnfamily would have one more guest to take care of. Thatrnwould be a total of 33. And the following year, 34. . .rnYou may object that America is not the only rich country inrnthe world; other rich countries would do their share, too. I’mrnnot so sure. No other nation has a statue like ours, with arnpoem like Lazarus’ on it. And now that immigrants are comingrnin hordes across their borders, other countries are gettingrntough. Unless the American mind undergoes a sea change,rnthe global burden of immigration is going to fall largely on usrn(as it has in the past).rnWhen it comes to philanthropy we Americans are prettyrnmacho in our attitude: we think we can save the entire world.rnMachismo, like most egotistic attitudes, blinds its holder tornthe true interests of others. Those who favor massive immigrationrnseldom stop to think deeply about the effects of theirrnwell-meant actions on the countries that furnish the immigrants.rnIn some cases we preferentially let in immigrants whornare highly trained in some skill or other. That may be fine forrnus, but it creates a “brain drain” from the country of origin. Irndon’t know how many physicians have come to us from Indiarnand Sri Lanka, but it’s a lot. You can hardly blame the immigrant-rndoctors for wanting to better their situation, but arernwe doing their native countries a favor by practicing this sort ofrngenerosity? Are India and Sri Lanka so well supplied withrnmedical care that they can afford to donate doctors to us?rnWe also need to think in terms of a “troublemaker drain.”rnAmong the 120,000 Marielitos there may well have been somernwho, had they stayed home, might have benefited Cuba byrnmaking trouble for Castro. It’s hard to know. But surely Castro’srndomination over his country was strengthened by ourrnacceptance of his rejects. And what about the Cuban peoplernthemselves—did the exodus help those who stayed home?rnOf course, whenever we play “what-if” history in terms ofrnbrain drains and troublemaker drains our conclusions rest onrnshaky ground. So let’s just assume that every army of emigrantsrnfrom a country is a random sample of its population.rnThat brings us to the purely numerical effects of emigration.rnSince out-migration reduces overpopulation, the ratio of resourcesrnto needs is changed in a favorable direction. Thernstay-at-homes are better off. What is their reproductive responsernto this improvement?rnHere we come to a controversial area. Studies of nonhumanrnanimals consistently show that improvements in living conditionsrnincrease the fertility rate. Curiously, the opposite conclusionrnwas asserted with respect to human beings early inrnthis century. The argument hinges on a correlation. LookingrnJUNE 1993/17rnrnrn