WHEN Japanese voters last week dealt a critical blow to their ruling Liberal Democratic Party (LDP), they moved their nation one step closer to maturity as an international superpower.

At first glance, the weakening of the Liberal Democratic and apparent ascendency of the Socialists suggests a further Japanese retreat from international involvement.

The elections cost the LDP control of the upper house of the Japanese parliament and brought down Prime Minister Sousuke Uno. Before the setback, the party had held a monopoly on government power in Japan since 1955.

The election turned on the Liberal Democrats' decision to allow more foreign agricultural goods into the country. Also at issue were taxes and Prime Minister Sousuke Uno's liaisons with geishas.

These inward-looking questions are not exactly the sweeping ideological issues which would foreshadow a major re-evaluation of Japan's global role. In fact, the Socialists are more isolationist than the Liberal Democrats--they even support a cancellation of Japan's security arrangement with the U.S.

But the turning points of the recent campaign and the specific policies of the Socialists are not likely to have a long-term effect on Japan's development. The real watershed is the birth of truly partisan politics in a previously apolitical Japan.

THE Socialists' inward-looking platform is not workable in an era when Japan's economic success is thrusting it into the international community.

Japan's pool of surplus capital being funnelled into other countries makes a retreat from foreign involvement impossible. Japanese investing abroad will demand that their government attempt to influence the policies and development of the nations where they have put their money.

As Japan is increasingly forced to look outward, the short-term impact of this year's elections will be minimal. The upper house is weak under the Japanese system, and all of the day-to-day decision-making power in Japan rests with the bureaucracy, not elected officials.

Nonetheless, this summer's election was one of the first truly democratic actions by the Japanese people since their current government was built up from the rubble and ashes of World War II.

As the Liberal Democratic Party tightened its stranglehold on power in the early 1950s, it moved to squelch the powerful labor unions that had formed in the economic chaos following the war.

Had the powerful unions won their colossal struggles with management and the government, a very different Japan would have emerged. Instead the backs of the unions were broken, the government and business began a symbiotic relationship and Japan Inc. was born.

The epitome of Liberal Democratic rule ever since has been preservation of the status quo. The ruling party's pro-business slant and its ability ensure political stability were large parts of the impetus for the Japanese economic dynamo. For more than three decades, Japanese economic prowess was synonomous with Liberal Democratic rule.

THAT success has been furthered by Japan's stubborn refusal to open its shores to foreign goods. This economic policy has been the most noticeable aspect of Japan's world view, but it has been accompanied by two other significant decisions--a refusal to spend much on foreign aid and a shying away from any military build up.

Since the disaster of the World War, the LDP has steered clear of any role in foreign affairs, prefering instead to build quietly the Japanese economy. The policy worked well for years as Japan filled the world with its products and kept foreign goods away from its shores.