STABILITY IS ALWAYS hard to build after a revolution, and particularly in a country that is, even by the Third World's standards, poor. Mrs. Aquino's democracy in the Philippines is now under challenge from both right and left. Great numbers of Filipinos evidently believed that the corrupt Marcos autarchy was an important part of the explanation of the country's condition, and, they reasoned, its overthrow would bring a great and dramatic change in their standard of living. But while the economy has been growing, the improvement has not yet been substantial. Mrs. Aquino is struggling to cope with the sense of disappointment that is the aftermath of revolutionary euphoria.

The attempted coup by dissident soldiers last week was the fifth since she came to office 18 months ago. On the left, she faces not only an entrenched communist insurgency but increasingly radical labor protests. Two days before the coup, the left organized the first general strike since the revolution. It was a demonstration against higher fuel prices and took place after Mrs. Aquino, in response to a wave of earlier transport strikes, had already rescinded half of the increase. The size of the strikes suggested that the left, badly beaten in the legislative elections last May, is gaining strength by exploiting dissatisfaction with slow economic progress.

Gasoline is not a commodity that ought to be subsidized by the government of a country whose people are mostly peasants, and mostly in great poverty. But the cities are sensitive to its price, and, in this test of wills, the organizers of the strikes were able to throw Mrs. Aquino, in a small but very visible way, off balance. In the past several days she seems to have recovered, under the far greater pressure of the dissident officers' plot to overthrow and, it appears, to assassinate her. Now that she has the initiative again, what is she to do with it?

Economic growth is going to be crucial. The United States, with Japan, the World Bank and others, is sending aid. There's a strong case for sending more of it, and for purposes that will show effects more quickly.

Otherwise there will be a rising danger of a vicious circle as slow economic growth aggravates political disorder, and political disorder frightens off the kind of investment, by both Filipinos and foreigners, that is required for faster growth. If the rich countries of the world want to show their support for a new democracy under great strain, this is the moment to do it