One has to wonder, now and then, about America's greatest corporations. Are their top people nuts? Are they subject to a kind of death wish? Are the managers intellectual eunuchs, lacking any sort of coherent political and economic philosophy?

The questions are prompted by a massive study, due out this week, from the Capital Research Center in Washington. For the fourth year in a row, Thomas J. DiLorenzo, professor of economics at the University of Tennessee, has examined corporate giving to organizations whose purpose is to influence public policy. We are not talking about gifts to the Boy Scouts, the Community Chest or the National Gallery.DiLorenzo sought information from companies on the Forbes 250 list. Of these, 146 companies responded. The other 104, for whatever reason, declined. Such big outfits as Disney, Apple Computers, Boise Cascade and General Dynamics replied stiffly that they "did not wish to participate in the study." Other big names - Food Lion, A&P, Houston Industries - refused even to return DiLorenzo's telephone calls.

Nevertheless, his data on the 146 major companies served to confirm patterns that he has seen before. Some of the nation's foremost business enterprises regularly contribute to organizations whose purpose is to inhibit business.

In a foreword to the study, Pete du Pont, former governor of Delaware, speculates on this suicidal phenomenon. Conservative industries continue to support liberal foundations, he suggests, partly because the old-line liberal outfits are "safe." The beneficiaries may not have produced a really creative idea in 20 years, let alone a good one, but giving to a risk-free foundation will raise no stockholders' eyebrows.

Other corporate giving, du Pont believes, is giving in self-defense. Jesse Jackson is not likely to call a boycott against a company that has just given his Rainbow Coalition half a million dollars. Some of the giving - or misgiving - may be a result of pure ignorance: Corporate managers have little idea of where their largess is going or what it is accomplishing.

Whatever the reasons, corporate giving is big bucks. DiLorenzo says the 146 companies contributed $28 million last year to public policy groups. In terms of total philanthropy, the amount is small, but "it is not unimportant, for the money given to such groups is highly leveraged."

The puzzling fact is that for every $1 given to groups that are generally pro-business, big business gives $2 to groups with a bias against business. These were the figures for 1988: to liberal groups, $17.5 million; to conservative groups, $8.6 million; to non-partisan organizations, $1.9 million.

For example, Dayton-Hudson, the Minneapolis-based retailer, gave generously to every liberal outfit that held out a tin cup. Such giants as AT&T, General Mills, American Express and Coca-Cola were angels to dozens of liberal think tanks and pressure groups whose aims were regularly opposed to business interests.

Conservative groups fared only so-so. Yes, Ford Motor Co. supported Cato, Procter & Gamble gave $50,000 to the Hoover Institution, and Lilly contributed $150,000 to the Hudson Institute. But the overall pattern was both clear and unclear. Ford's gifts were all over the philosophical lot; the company supported a little bit of everything.

DiLorenzo's findings boggle the mind. Why should a company whose future depends upon preservation of the enterprise system make large donations to organizations out to undermine the enterprise system? Hand me a shovel, say these corporate executives, and let me dig my own grave.