Where Hart gets his 'new ideas'

THE sudden, unexpected, and dramatic emergence of Sen. Gary Hart on the American political horizon has set observers the world over to asking themselves and each other who he is and what he stands for. We have not yet defined his ideas clearly. We are all groping for a definition.

Here is my contribution to the effort to find definition.

His use of the phrase ''new ideas'' has confused rather than clarified. I have not yet uncovered in his public statements what seems to be a truly ''new'' idea, theory, or doctrine. But a scanning of the record suggests that he has come up with something more interesting than ''new ideas.''

Out of his experience he has done a job of sorting through the political ideas of both the old ''liberal'' Democrats and the new ''conservative'' Republicans, rejecting much from the first and selecting some important items from the second to put together a new composition that clearly is making sense to a lot of voters, particularly those under 45.

The extent to which he has selected from the ''conservative'' side of the American political spectrum is obscured in part by the necessity he is under to keep his distance from Ronald Reagan. He must at least appear to be against almost everything Mr. Reagan stands for. Yet the fact is the senator has fitted into his own political platform two essential features of Mr. Reagan's domestic policies. These are (1) the importance of modernizing and revitalizing the US economic structure and (2) cutting income and inheritance taxes and curbing welfare as important means to that end.

This is what has forced him into an open break with organized labor. He opposes ''domestic content'' legislation, a new word for trade protectionism. He favors business, but he wants it to be competitive business. Hence, he is happy with the deregulation which has broken up such old protected activities as airlines and trucking routes. There can be little doubt that deregulation has helped to modernize American industry.

He agrees with Mr. Reagan on the importance of an effective national defense, but differs over methods. He wants more money put into training, combat readiness, conventional battlefield weapons, and stockpiling of ammunition. But he wants to cut out those expensive superweapons which are beloved by the defense contractors but are controversial among the military users. These include the B-1 bomber, the M-1 tank, the MX missile and the superair-craft carriers. All of these have been opposed in some reputable military quarters.

He differs with Mr. Reagan over the use of military power in support of foreign policies. He thinks Mr. Reagan has overrelied on force in places where, he suggests, either diplomacy or economic aid could have been more effective.

His ideas about military weapons would fit better with those of the current NATO high command than with those of the Reagan White House. The NATO command favors emphasis on development of conventional military power. It wants to be able to defend Europe without having to resort to nuclear weapons. Senator Hart's proposals would fit.

He differs with Mr. Reagan also over nuclear policy. He wants emphasis on negotiations to freeze and reduce weapons rather than to build more new ones.

In other words, the assortment of ideas with which Senator Hart has attracted a remarkable turnout of young voters represents a selection from among both old Democratic and current Republican political cupboards. The selection cannot fairly be called either left or right. It reflects an attempt to discard from both camps ideas which events have proved unsound while selecting from both those ideas which have a better chance of making the US more vigorous and competitive in the future.

I do not suggest this is necessarily the best selection which could be made. Nor have I any way yet of judging how much of what the senator proposes could be put into practice by him or by anyone else in the presidential office. But certainly much in the old ''liberal'' Democratic program has proved wanting, and some of Mr. Reagan's new conservatism has been abandoned by Mr. Reagan himself. Mr. Reagan, for example, is dedicated now to ''environ-mentalism.'' So is Senator Hart.

Political progress proceeds from thesis to antithesis to synthesis. The New Deal was a thesis. Reaganism was an antithesis. Senator Hart has put together an attempted synthesis of the best of both. There can be no doubt about its appeal.