Dear Dinah: Sounds like your solo in the Boston church was a triumph. Your grandma and I wish we could have been there to hear it. We’ll make it some time.

Now to defend myself against your charge that I’m just an old Scrooge when it comes to immigration. To Cain’s question “Am I my brother’s keeper?” you say that the answer has to be an unqualified “Yes.” Your position has distinguished supporters. There’s the poet Schiller, for instance, in his “Ode to Joy,” which you know from Beethoven’s Ninth (since you’ve sung in the chorus). And Walt Whitman. And most of today’s professional philanthropists. It is also what most Americans think our Statue of Liberty says. But they’re wrong.

We’ve been brainwashed by that darned poem on the base of the statue. Emma Lazarus, pretending to speak for all Americans, said: “Give us your tired, your poor, your huddled masses.” How inspiring! How magnanimous of us to offer to share our wealth with all the world’s wretched! But who made this commitment? Our own poor, our unemployed, our homeless? Not on your life. The poet was a wealthy woman, who proposed sharing the wealth, the jobs, of other people—our poor—with an unlimited number of immigrants.

As a matter of historical fact, the poem is not a proper part of the statue. It was added to the base 17 years after the statue was dedicated. And who added it? Congress? No, some of Lazarus’ wealthy friends put it there. Congress wasn’t consulted. Neither were the homeless and the unemployed. Nor Americans working on the lowest rungs of the economic ladder, where they can easily lose their jobs to new immigrants. The wealthy don’t suffer from such “generosity.” In fact they often gain by being able to hire cheaper servants.

Many fine people sincerely think we should dismantle the borders around our country, letting in all who want to come. I don’t quarrel with their intentions: they mean well. But they need to mind the “p’s and q’s” of immigration, or else they’ll do more harm than good in the long run.

I don’t know the origin of the expression “p’s and q’s,” but when it comes to immigration the two letters can stand for precedents and quantities. These are the p’s and q’s of immigration that we must pay attention to. President Carter learned the importance of precedents when, good Christian that he is, he welcomed the Cubans fleeing Castro’s dictatorship in the “Mariel boatlift” of 1980. In a few days the numbers amounted to 120,000, and Carter backpedaled from what he had mistakenly thought was a Christian imperative. The number 120,000 happened to be the exact amount of population increase in one year in Cuba. The President’s advisors no doubt pointed out that Cuba could easily send us that amount every year—forever. Moreover, to bring the island’s population down to its carrying capacity Castro would have to send more than 120,000 per year. In which case, as the less crowded islanders became more comfortable, they would no doubt practice contraception less conscientiously, thus allowing fertility to rise and producing even more candidates for emigration.

Then, as other overpopulated nations—overpopulated in the judgment of their own people—became aware of the precedent set by the Cuban boatlifts, they too would dump their surplus populations in Uncle Sam’s lap. It took less than a month for President Carter to realize the insanity of acting on what appeared to be Christian ethics. The President then let it be known that the Mariel boatlift was a one-time thing. Thus did he, in effect, warn the 10 million people of Cuba, the 6 million people of Haiti, the 5 million people of the Dominican Republic, the 5 million people of El Salvador, the 7 million people of Guatemala—and hundreds of other millions —that they should not expect the United States to dismantle its borders just because their people are in need. (These are the figures for 1980; since then the populations of these countries have increased by 24 percent, while the population of the United States has grown by only 15 percent.)

I would argue that the acceptance of unlimited numbers of immigrants only appears to accord with Christian principles. Is this where you and I have a difference of opinion? Let me state my position, and you can tell me where I’m wrong.

I approach immigration problems from the scientific side. As modern science emerged in the 17th century, Galileo said that “the grand book of the universe is written in the language of mathematics.” Believe me, this is a central dogma in the faith of all scientists. Time after time a difficult question that does not obviously involve mathematics yields its secret once mathematical reasoning is introduced. Such successes lead some of us—I’m one—to believe that the discipline of ethics can also benefit from mathematical insights. We must pay attention to quantities—the “q” of our “p’s and q’s.” I think there are many instances in which dealing quantities into the game—even in a rough way—permits us to reinterpret traditional ethics in a manner suitable to practical men faced with practical problems.

When Cain asked the Lord “Am I my brother’s keeper?” he was obviously thinking of only one brother, Abel (whom he had just liquidated). I don’t know anything about Hebrew, but in English the very printing of the question confines the conclusions to the singular case—”brother’s.” To go from the singular to the plural case, in English, you have to write “s” apostrophe, i.e., “my brothers’ keeper.” As far as ethics is concerned, perhaps the difference between one brother and two would not be enough to bother about. But suppose there are a million brothers. Ten million. In all realism, must I be “my brothers’ keeper” when there are hundreds of millions of brothers out there crying to be cared for? Quantities matter.

What we call the “poverty line” in annual income is an arbitrary figure, but by any evaluation reasonable to Americans, two billion people throughout the world live below the poverty line. (Or maybe they only exist at that low level.) The trouble with large numbers like a million or a billion is that the human mind does not easily grasp their implications. We need to find a simple way to reduce large numbers—and large obligations—to the human scale. In the present instance. that’s easily done.

A population of two billion wretchedly poor in the world is roughly eight times as great as the total population of the United States. To get a feeling for the load this would create, let’s imagine that the problem is handled at the family level. Dinah, you come from a family of four—pretty typical for our country. If our 250 million people took in two billion immigrants, that would mean each family’s share would be 32 immigrant-guests to be invited into its home. Of course we wouldn’t do it that way: instead we would pay taxes to achieve the same end. But I assure you that the total burden would not be lessened by using taxation to deal with it. Whether in our homes or outside them, we would have to house, feed, clothe, educate, and find jobs for two billion immigrants. And if the guests maintained the fertile habits of their homeland (as they undoubtedly would), the next year each American family would have one more guest to take care of. That would be a total of 33. And the following year, 34 . . .

You may object that America is not the only rich country in the world; other rich countries would do their share, too. I’m not so sure. No other nation has a statue like ours, with a poem like Lazarus’ on it. And now that immigrants are coming in hordes across their borders, other countries are getting tough. Unless the American mind undergoes a sea change, the global burden of immigration is going to fall largely on us (as it has in the past).

When it comes to philanthropy we Americans are pretty macho in our attitude: we think we can save the entire world. Machismo, like most egotistic attitudes, blinds its holder to the true interests of others. Those who favor massive immigration seldom stop to think deeply about the effects of their well-meant actions on the countries that furnish the immigrants. In some cases we preferentially let in immigrants who are highly trained in some skill or other. That may be fine for us, but it creates a “brain drain” from the country of origin. I don’t know how many physicians have come to us from India and Sri Lanka, but it’s a lot. You can hardly blame the immigrant-doctors for wanting to better their situation, but are we doing their native countries a favor by practicing this sort of generosity? Are India and Sri Lanka so well supplied with medical care that they can afford to donate doctors to us?

We also need to think in terms of a “troublemaker drain.” Among the 120,000 Marielitos there may well have been some who, had they stayed home, might have benefited Cuba by making trouble for Castro. It’s hard to know. But surely Castro’s domination over his country was strengthened by our acceptance of his rejects. And what about the Cuban people themselves—did the exodus help those who stayed home?

Of course, whenever we play “what-if” history in terms of brain drains and troublemaker drains our conclusions rest on shaky ground. So let’s just assume that every army of emigrants from a country is a random sample of its population. That brings us to the purely numerical effects of emigration. Since out-migration reduces overpopulation, the ratio of resources to needs is changed in a favorable direction. The stay-at-homes are better off. What is their reproductive response to this improvement?

Here we come to a controversial area. Studies of nonhuman animals consistently show that improvements in living conditions increase the fertility rate. Curiously, the opposite conclusion was asserted with respect to human beings early in this century. The argument hinges on a correlation. Looking over the nearly two hundred nations one notes a negative correlation between fertility rate and prosperity: rich nations have lower fertility than poor ones. Such a correlation is consistent with both of two hypotheses: either high fertility causes poverty or prosperity causes low fertility.

Logically, these contradictory hypotheses are equally defensible. They are not, however, equally “acceptable” to most kindhearted people. For more than 40 years the second one dominated public discussion. Why? Because it leads to the conclusion that we should be able to get poor countries to lower their birthrates by “throwing money at them,” a conclusion that leads to employment for professional philanthropists. “Foreign aid” also brings profits to the American entrepreneurs whose exports are bought with our tax funds.

If, on the other hand, high fertility causes poverty, we have to tackle the problem of persuading poor people to change their “family values.” This is difficult. That’s why popular opinion, for nearly half a century, favored the idea that the human species, unique among the millions of species of animals, irrationally maximizes its fertility when attempting to escape hard times. Since 1975 real population professionals have abandoned the error. (The press has not yet caught up with reality.) Demographers now admit that the immediate effect of making poor people suddenly richer—better fed and more optimistic—is to increase their fertility.

Nevertheless, a last-ditch counterargument has surfaced. It is claimed that the immediate effect of greater income—fertility enhancement—will wear off in a generation or two. Maybe so; but in two generations high fertility can do a lot of damage to a poor country. At the present rate of growth world population could more than double in two generations. (How would you like to drive your little car around a Boston that has twice as many people in it? If things keep going the way they are now, you soon will.)

The bottom line is this: the days are over when in-migration could be defended as a solution to any national problem. Japan has known this all along. From a narrowly national point of view, emigration—out-migration—may be a solution of sorts to national problems. But immigration harms the receiving nation directly and the source nation indirectly because it weakens the motivation to solve problems on the home front. Australia and the European countries are now painfully recognizing the perils of immigration. To become rational about immigration Americans need to disown the appalling advice of Emma Lazarus. The philosopher Alfred North Whitehead once remarked that “through and through the world is infected with quantity. To talk sense, is to talk in quantities.” Traditional ethics is right when it says that we can, and should, be our “brother’s keeper.” But so massive and uncontrolled is the growth of poor populations that it is literally beyond our means to be our “brothers’ keeper.” While apostrophe “s” defines a possible virtue, “s” apostrophe is an impossible one. Quantities are important. Numbers matter. Ethics must become numerate, quantitative.

I don’t want to get you in trouble with your friends, Dinah, but you might just float a few of these balloons over their heads. Tell them that you “know an old codger out West who says”—then mention one of these points. But distance yourself from the argument: there’s no reason for you to take the heat. Let me know their replies; they should be interesting.