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Mr. [Freeman J. Dyson]'s main case for ''diversity'' comes from biology, which, by its very nature, is more diversified than physics. Only Darwin's theory of natural selection, or perhaps the discovery of the genetic code as revealed primarily through the work of Francis Crick, can qualify as profoundly unifying. Among other things, Mr. Dyson cites the theory of ''genetic drift'' of the Japanese geneticist Motoo Kimura, who believes that random statistical fluctuations in evolution have been more important than Darwinian selection. Mr. Dyson addresses a question I have always found puzzling: Why is life so complicated? If simple elegant solutions to problems are the best, then why does nature need go to the lengths she does in order to produce viable living structures such as ourselves? Mr. Dyson's answer lies in ''homeostatic systems'' - systems that maintain a constant local environment despite changing external conditions. He argues that homeostatic systems are a necessary prerequisite for life and that such systems are necessarily complicated, relying on diversity to maintain their equilibrium. He applies this belief particularly to space research, arguing that the scientific values of missions in space have been more or less inversely proportional to their cost. He believes that it will be possible, in the dim but not too distant future, to use genetic engineering to design creatures that can exist and be self-supporting in space. Unabashed by the science fiction nature of such suggestions, he presents his ''scavenger turtle'' (with diamond-tipped teeth), ''energy tree'' and ''mining worm.'' His centerpiece is a one-kilogram spacecraft ''astrochicken,'' which will be ready to launch in 2016. It will not be built but grown by the use of genetic engineering, and it will depend on artificial intelligence and solar-electric propulsion for its operation. Accompanying it will be a ''Martian potato,'' a ''comet creeper'' and a ''space butterfly.'' He has a great faith in the value of artificial intelligence, but believes that human intelligence will ''remain far ahead . . . as far into the future as I can imagine.''

All American thinking about nuclear weapons is strongly influenced by two popular myths surrounding their origin. One myth says that nuclear weapons were decisive in winning World War II. The second myth says that if Hitler had acquired nuclear weapons first, he could have used them to conquer the world. Both myths were believed by the scientists and statesmen who built the first nuclear weapons. They are still believed by most Americans today. These myths have created the unexamined background for later American doctrine concerning nuclear weapons. Nuclear weapons are seen as militarily decisive (because we won) and historically justified (because Hitler might have conquered the world). If a political arrangement is to be durable, it must pay attention both to technical facts and to ethical principles. Technology without morality is barbarous; morality without technology is impotent. But in the public discussion of nuclear policies in the United States, technology has usually been overemphasized and morality, neglected. It is time for us now to redress the balance, to think more about moral principles and less about technical details. The roots of our nuclear madness lie in moral failures rather than in technical mistakes. Our thinking is permeated by our historical myths. We tend to accept without serious question the idea that nuclear weapons are militarily decisive. We usually equate military effectiveness with destructive power. We rarely examine critically the military purpose of nuclear weapons or the possible missions for which they might be used. The case for the feasibility of abolishing nuclear weapons would be stronger if we treated them with less respect. The hope of successful abolition becomes more realistic if it is understood that nuclear weapons are absurd rather than omnipotent.

LEAD: Diversity in Hiring From remarks Jan. 6 by Prof. Alan Freeman of the State University of New York at Buffalo at the convention of the American Association of Law Schools in New Orleans. Professor Freeman spoke on behalf of 300 colleagues who had signed a petition calling for the appointment of an independent commission to promote ''diversity in hiring'' in law schools. Diversity in Hiring From remarks Jan. 6 by Prof. Alan Freeman of the State University of New York at Buffalo at the convention of the American Association of Law Schools in New Orleans. Professor Freeman spoke on behalf of 300 colleagues who had signed a petition calling for the appointment of an independent commission to promote ''diversity in hiring'' in law schools.

Scientists since the time of Linnaeus have given scientific names to and characterized to some degree about 1.4 million species of plants, animals and microorganisms. But the estimates of the actual number that exists range, according to the models employed, between 5 million to 30 million and more. In other words, we don't know to the nearest order of magnitude how many species of organisms there are on the planet. And furthermore, we don't know why there are that number of species and we don't really understand fully why there are more species in certain parts of the world such as the tropics. This is a critical problem because the habitat destruction around the world, particularly in the tropics, is reducing that diversity rapidly through species extinction. . . . That whole area is not covered by Nobels. It matters because the Nobels tend to call public attention in a dramatic fashion to outstanding scientific problems and attempts to solve them. So this, I believe, is a substantial shortcoming. - E. O. Wilson, biologist, Harvard University Beyond Piaget I don't believe that social psychology is really a science in the capital 'S' sense. I think it's part of anthropology and sociology, what I call cultural studies. What's left is the area that people like Freud and William James were very interested in -personality, will, consciousness, stuff like that. My own feeling is that is not so separate from literary studies. . . . According to a classic principle of economics, people are ''optimizers'' who constantly attempt to maximize economic gains. Many psychologists, however, don't believe people work in so tightly rational a manner. Is economics ready to be called a science, or does it occupy some lower realm?

Since the American armies were demobilized after World War II, nuclear weapons have served as a relatively inexpensive means of filling the gap between the forces of the North Atlantic Treaty Organization and the vast armies of the Warsaw Pact. From the earliest ''ban-the-bomb'' movements, through the halcyon days of arms control during the 1970's, to Mr. [Ronald Reagan]'s vision of a nuclear-free world sheltered beneath a leakproof ''space shield,'' the nuclear guarantee - under which the United States would respond to a Soviet invasion of Western Europe by launching its missiles - has remained the crucial link between America and its allies.