How ideas influence the economy; The Economy in Mind, by Warren T. Brookes. New York: Universe Books. 240 pp. $15 .95.

To oversimplify drastically, there are two types of conservatives. The first group are ideologues who do little fresh thinking, merely spouting conservative or even reactionary doctrine. They're often called ''troglodytes'' or are dismissed with some similar put-down by their critics.

The second group can be equally conservative, but they do their homework. They back up their views with research and thoughtful analysis. This second group is more numerous today. Its members can be found working for such institutions as the American Enterprise Institute or the Heritage Foundation. Their research and publications have dramatically elevated the level of public debate between liberals and conservatives.

Warren T. Brookes, an economics columnist for the Boston Herald American, is definitely a member of the second group. His book, commissioned by another conservative think tank, the Manhattan Institute for Policy Research, does argue for many of the traditional conservative positions. Mr. Brookes attacks the progressive income tax. He laments much of government regulation. He criticizes large government deficits and the creation of too much money. He supports some supply-side economics. He backs a gold or commodity-backed monetary system. He urges a drastic tax reform called the flat-rate tax. He even defends ''trickle-down economics,'' the view that if the well-to-do are prospering, some of their money will trickle down to benefit the poor also. All these Mr. Brookes does well, because he backs his views with arguments, studies, facts, tables, and charts.

Like many writers on economics, however, Mr. Brookes often makes his case too strongly, ignoring or underplaying the usual trade-offs in economics. Middle-ground economists, as well as liberals, could have a lively time taking pokes at the support behind many of Mr. Brookes's positions, coming up with counterarguments or even counterfacts.

Nevertheless, Mr. Brookes's book is most notable for something that sets it apart from other books on the subject: its attempt to tackle economics from a ''metaphysical'' basis. ''. . . wealth is at its root metaphysical (the product of ideas and the promotion of useful qualities and values),'' he writes; ''purification and spiritualization of thought are not merely Christian ideals, they are at once the keys to human prosperity and economic progress, and the disciplines that make human freedom possible and capitalism compassionate.''

He goes on: ''In other words, goodness and purity of thought are not merely the stuff of Pollyanna religion or of positive thinking, they are substantial economic assets, the most fundamental components of our real GNP (gross national product - the total value of goods and services produced in a nation); and they will grow even more important as this nation moves progressively into an economy based on the components of mind more than on the elements of matter.''

A number of economists have noted the importance of mental factors to the economy. Education is usually regarded as the most important element in increasing productivity. Wise decisions by policymakers promote national economic welfare. Poor morals could be regarded as a cost burden on the economy in several ways. Business and home must ''waste'' money on protecting themselves from crime. The abuse of alcohol or drugs saps the productivity of workers. Homes broken by immoral behavior or loose marriage standards add to the nation's welfare burden, as single mothers try to cope with poverty.

But Mr. Brookes goes beyond that. He is saying that, under a God who is Love, human prosperity is the ''inevitable result'' of high moral and spiritual standards, understanding, and progress. As evidence, he cites biblical incidents - manna from heaven sustaining the Jews in the wilderness, oil continually flowing from a container (cruse) providing for a widow and her sons, Christ Jesus feeding the multitudes with five loaves and two fishes, and so on.

The prosperity of today's capitalist economies, such as that of the United States, arises from the freedom their economic systems give individuals to be innovative and to take constructive risks. This national wealth hangs on faith in the future - the ''substance of things hoped for,'' he writes, again quoting the Bible. ''Without faith, without confidence, wealth is not generated, risky investments are not made, crops are not planted, businesses are not founded, and poverty ensues.''

It is when he applies this basic faith in God's provision for His children to current affairs that Mr. Brookes becomes both fascinating and controversial. In fact, some of those also with strong convictions of God's love for man may regard some of Mr. Brookes's positions as unwise or just plain wrong. When an individual with firm religious views applies his theology to human affairs, there is a danger he will equate his political or economic views with the divine will. He may decide, say, that ''God is a Republican and a capitalist to boot.'' Mr. Brookes doesn't go that far, but he goes in that direction sometimes.

For example, because of his faith in the power of ideas to generate wealth, Mr. Brookes attacks the popular view that there are material limits to growth, such as those limits expounded in the much-touted Global 2000 report that came out during President Carter's presidency or those limits that are the subject of concern in some ''liberal'' Christian churches.

''Our economic future,'' Mr. Brookes writes, ''is not now and never has been tied to the physical assets we now see, but to the vast untapped potential of creative thinking - the metaphysical process which can show us entirely new reserves and new and easier ways of doing things, extending value and increasing wealth without depleting our planet. The only impediment to this is a fearful or limited concept of the real source of our wealth, a lack of faith in our ability as free individuals and institutions to generate whatever we need and to allow new ideas to unfold and new processes and resources to develop - in short, to continue to explore the unlimited economy that exists in mind.''

OK, but could it not be that the right ''new ideas'' may be ones about greater conservation or changed life styles that are less ''materialistic.'' Or maybe the right idea is a mixture of conservation and the discovery of new resources or techniques. Or it could be that the world has not yet advanced mentally to the point at which it, figuratively, can always find coins in the mouths of fish. There remain dangers of food and resource shortages. The point is, there is room here for widely varying human opinions.

Similarly, Mr. Brookes backs great enlargement of immigration into the United States. ''Our national economic growth will indeed be limited if we fear and so deliberately limit population growth, or in other ways hinder the freedom of our 'individual capital' to develop itself. We cannot protect our own economic position by limiting the access of others.'' Undoubtedly, immigrants have brought great wealth in the form of ideas and hard work to this country. Nonetheless, it could still be the lesser evil to halt the ''brain or brawn drain'' from other nations.

In many areas of public policy, the choices are not often as clear-cut as Mr. Brookes paints them.

Nonetheless, this book is so bubbling with ideas (many of them good ones), with challenges to standard liberalism (which may be as doctrinaire as standard conservatism), with citations of fresh research, and with a moral vibrancy badly needed today, that it is stimulating and important.

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