IT'S AN interesting question: How would you use a billion dollars to help the poor? Harry Weinberg, who grew up in Baltimore and began building his immense fortune there, has left nearly all of it to a foundation with little more than the commandment that it is to benefit poor people. With undisguised hostility to the world of the graces, he added that none of his money was to go to colleges -- he himself had dropped out of school in the sixth grade -- or to museums or orchestras.

A quarter of the proceeds are to go to philanthropies that help the Jewish poor -- although he set a firm limit on gifts to Baltimore's Jewish Community Federation -- and another quarter to philanthropies that mainly help the non-Jewish poor. The rest is to go to the poor without regard to creed or race. Those terms leave the trustees considerable latitude. The foundation's good works won't be limited to Baltimore, but much of its effort will be focused there.

Mr. Weinberg was a rough-hewn spirit who drove old cars and saved money on his clothes. For many years he was a thorn in the flesh of the people trying to improve Baltimore, for he owned a lot of run-down property that he resolutely refused either to renovate or sell. He cared nothing for appearances.

There are, broadly speaking, two ways to help the poor. One, in the ancient tradition, is to feed the hungry, shelter the homeless and care for the sick. The other is to try to change the circumstances under which people who are born poor remain in that condition all their lives. Private philanthropy can experiment more boldly than government money can, working to influence social attitudes and public policy. The Weinberg Foundation will have the resources to do both.

This enormous bequest is great good fortune to Baltimore and to those of its people most in need of a little luck. It arrives at a time when this country's poor are getting poorer in relation to the rest of the country, while its government seems to have run out of ideas -- and run out of interest as well -- in doing much about it. The subject of poverty is not in fashion these days. But Mr. Weinberg would have been pleased to be out of fashion in the giving of this great gift.