Sen. Gary Hart (D-Colo.) yesterday urged the Democratic Party to adopt a philosophy of government he called "aidez faire -- to help make happen," in contrast to the Republicans' laissez-faire economic policies.

In outlining his "foundation for an American renewal," Hart also called on Democrats to push for military reform and suggested a research project with the Soviets on the level of World War II's Manhattan Project to "devise new ways to guarantee" compliance with nuclear arms agreements.

A Democratic government "must be a catalyst government that sparks the fires of change," he said in the second in a series of speeches in which he plans to spell out a new agenda for the Democrats. The first was delivered in Boston in February.

Hart, runner-up to Walter F. Mondale for the Democratic nomination last year, has said he will make no decisions about his future until year's end. However, his speeches are widely viewed as groundwork for a 1988 presidential campaign.

"The Party of Progress," he told an audience of American University students, "has come to worship the status quo . . . . We too often protect old programs rather than old values."

Democrats must foster an "investment strategy in long-term economic growth and opportunity . . . . Social justice is inseparable from economic growth," he said.

"We will not achieve growth and opportunity merely by relying on the market, as this Republican administration advocates. Markets can drive our economy, but they cannot calculate the national interest . . . .

"Aidez-faire, not laissez-faire -- to make change happen for the benefit of all, not to let things happen for the benefit of the few."

Calling the American military "the victims of technology," he said Democrats must redefine national security in an era of global change.

"The party that pioneered innovations in our social institutions must now pioneer reforms that will bring excellence to our military institutions," Hart said. ". . . All who acknowledge there are legitimate and necessary uses for American military force should seek to make that force as effective as possible."

Despite the rise of nationalism, radical religious fundamentalism, the spread of nuclear weapons and the accumulation of an explosive Third-World debt, he said, the Reagan administration views the world "through an East-West ideological prism that obscures these historic changes . . . . Indeed, our security is betrayed by tired leaders who cling to an anachronistic view" that equates security and patriotism with a nuclear weapons buildup.

Hart recalled that President John F. Kennedy, in a 1963 speech at AU, successfully challenged the Soviets to join in halting atmospheric nuclear tests. He proposed "chal- lenging the Soviets again," to break "the technology-driven cycle of testing, production, deployment and then negotiation."

Since any treaty rests on the ability to verify it, he said, "we should also challenge the Soviets to join us in a Manhattan Project for Verification. Like the pioneering effort that produced the first atom bomb, this project can join the two largest scientific communities on earth to devise new ways to guarantee treaty compliance and prevent nuclear treachery."

He also proposed a "joint crisis-control center, staffed by senior military and diplomatic personnel from both superpowers" to analyze threatening conduct on either side and "prevent nuclear catastrophe by mistake."

In our conventional forces, he said, "Today, unfortunately, our military priorities are so distorted, we could well suffer a major defeat if challenged."