BECAUSE David Finley had retired 21 years before his death yesterday, perhaps only a few of the visitors to the National Gallery will recall his name. But all of them owe him a debt of gratitude. He was the Gallery's first director, and he had a speical genius for persuading the great collectors of his time to part with their pictures in behalf of a greater collection for the national capital. It was a style of patriotism now a little out of fashion, but the present generation of Americans is greatly its beneficiary.

The original idea for the Gallery, and the money, came from Andrew Mellon. The technical expert in the small group that established it was John Walker, who succeeded Mr. Finley as director. Mr. Finley's special contribution was a single-minded enthusiasm and a truly virtuoso skill in what you might call the diplomacy of art. After Mr. Mellon's death, the world's most important privately owned collection was held by Samuel Kress. Not many people realized the scale of the Kress acquisitions, but Mr. Finley heard of it and paid a call on Mr. Kress in New York. He arrived at three o'clock on a winter afternoon in 1938 (according to Mr. Walker's history of the Gallery) and stayed until 10 p.m. In the course of those seven hours, he persuaded Mr. Kress to abandon the private museum already being designed for a site on Fifth Avenue. Instead, the Kress Collection came to Constitution Avenue, where people who work downtown can now visit on their lunch hours.

The National Gallery, which opened in 1941 came along very late in the history of art collecting and museum-building. By the time that Mr. Finley came into the field, few paintings of great historical value were on the market. As a consequence, Mr. Finley collected collectors. Others whose names you can see on the frames at the Gallery include Lessing Rosenwald, and Peter and Joseph Widener - all of them (as Mr. Walker points out) Pennsylvanians like Mr. Mellon and Mr. Kress. To a remarkable extent, the Gallery is a Pennsylvanian gift to the nation.

Amidst contemporary Washington's wealth of galleries and theaters, it's difficult to recall how pinched and precarious a life the arts led here a generation ago. What the city had was mostly brought here by outsiders - imposed on the city by cultivated Americans from other regions, indignant to find the national capital living like a village of politicians and clerks. Painting was the first of the arts in which Washington came to enjoy truly first-class resources, and the museum collections set the standard for the remarkable numbers of painters who live and work here today. Mr. Finley devoted his career to a special definition of civilization, and his success is marked by the fact that the Gallery is full of people every day who now take that definition for granted.