Julian Simon has managed to make a living doing practically nothing that he trained to do. He is, first and foremost, a writer; but he is known mostly as an economist, though he has no formal economic training. At present he is a professor of economics at the University of Maryland and a senior fellow in resource economics at the Heritage Foundation. His expertise is in immigration policy, and he has emerged as one of the most skillful and persuasive critics of immigration restrictions. But his background is by no means irrelevant to his work.

The Navy ROTC sent Simon to Harvard to do his undergraduate work in experimental psychology-an experience he calls "a mixed blessing." After three years in the Navy, he almost went to medical school but instead went to work as an advertising copywriter. He then put in six months at Ziff-Davis Publishing, selling and promoting magazines.

In 1957, Simon decided to get an M.B.A. at the University of Chicago but ended up with a Ph.D. in business three years later. His thesis was in university-library management, so, typical of Simon's quixotic career jumps, he set up a mail-order business.

Several years later, he was teaching advertising at the University of Illinois but realized that writing was what he liked most. So he decided to dedicate himself to it. "I realized then that I was a writer, but I wanted to be both a writer and a scholar. Research-grubbing for facts, ideas, theoretical formulations-is part of that process.

"My experience in business played a great part in my approach to economic problems,'' says Simon, "partly because you can't be in business without seeing that there are all kinds of problems that aren't in economic models. In a way, I have benefited from my lack of economic training, because economists tend to approach problems from a scientific point of view. Scientists try to explain some puzzling aspect of nature, while people in business, like engineers, are more interested in finding the consequences of changing some variable."

Simon's first scholarly work-mostly critical-was on the economics of advertising. (And Simon was the first to do statistical work leading to the estimate that smoking one cigarette shortens your life by 5 to 9 minutes.) His second book was a "how to" book on research methods for social scientists, and his third was another book on advertising, which ended with the conclusion that, too much research had already been done on the subject and that the really important issues are ethical and aesthetic.

In the past few years, Simon has changed his mind about advertising, largely due to the influence of free-market economist Friedrich Hayek. "Some sorts of advertising are very important," Simon now says, "such as classified and industrial, and the rest is irrelevant and not an important area of inquiry."

His interest in immigration started during the population panic of 1969-70. He read a New York Times article on the population explosion and "enlisted in the good fight to stop it, using all my marketing skills." But, being a meticulous scholar, he researched the subject and came across Simon Kuznets's work on the subject. "He was my first real teacher," says Simon, "even before I ever met him." Simon kept his zeal for the population issue, but he wrote from a point of view exactly opposite that of the Malthusians, who were convinced, says Simon, "the world would shortly go up in flames."

Simon's groundbreaking work on the population issue was treated with hysterical indignation and accusations.

He even admits to one fist fight with a prominent so-called scholar. And as he dealt with one issue after another, explaining each into irrelevance, others were raised.

He says, "I was led from living space to resources to forests to water and on and on. There is no end to the objections people have to increased immigration." His main scholarly work on the subject is The Economics of Population Growth, published by Princeton University Press in 1977, but it was The Ultimate Resource, a less-academic work published by Princeton in 1981, that really shook things up. Its reception "exceeded my wildest expectations," Simon recounts. "The best part was the screams of the environmentalists. They assailed both my motives and my intelligence."

Simon likens his sudden entrance into the public eye to a bum sneaking into a posh Manhattan restaurant and being greeted with a magnum of champagne and a cigar. And he is still enjoying his new-found influence on immigration thinking. "Within the range of human experience," he says, "there has never been an influx of immigration that was too much for society to handle. There are really no good reasons for restricting immigration, and there are excellent reasons for allowing it."

According to Simon, many of the reasons people oppose immigration have more to do with psychology than economics. Part of the problem, he says, "is that moving but mischievously misleading poem by Emma Lazarus on the bottom of the Statue of Liberty. Immigrants were never tired, poor, huddled masses. The media are also a major problem, showing pictures of immigrants behind chain-link fences looking like caged animals. They never show pictures of the same people three months later, working two jobs to support their families while studying English on the side. Immigrants are, on the average, as well-educated as natives and actually contribute more to the social-welfare system than they take out. They are, in truth, the ultimate resource."

Patrick Cox is a frequent guest columnist for USA Today and public affairs director of the Pacific Institute for Public Policy Research.