SEN. HENRY M. JACKSON, who died Thurs day night at his home in Everett, Wash., showed a consistency and clarity of purpose unusual in politicians. First elected to the House in 1940 and then to the Senate in 1952, he was one of the few members of the current Congress to have served before Pearl Harbor. From those days, Mr. Jackson drew the lesson that freedom depends on preparedness and military strength.

He was interested from the beginning in nuclear energy and atomic weapons, and he believed that the United States must never let the Soviets gain advantage. That theme runs straight through his service on the Joint Committee on Atomic Energy in the 1940s. It explains the defense commitments he extracted for supporting the limited test ban treaty and the conditions he demanded for supporting the first strategic arms agreement--otherwise neither would have been ratified--as well as his misgivings about SALT II.

From the beginning, he was interested as well in natural resources and the environment. He turned down the position of undersecretary of the interior in 1950, and he was a force behind environmental laws in the 1970s. As chairman of the Senate Interior Committee, he balanced environmental and economic interests skillfully.

On domestic issues, he started off as "a 100 percent New Dealer" and never wavered in his faith that an active federal government could improve the lot of the ordinary person. But he always understood that government could abuse the civil liberties of its citizens. In his first years in the Senate, he stood up to Joe McCarthy when few others dared, never flinching.

He ran unsuccessfully for the Democratic presidential nomination in 1972 and 1976. But he gained in his career a more elusive victory: ideas he championed have held up over time. In the last four decades, Americans and their government have generally advanced freedom, increased prosperity and improved the quality of life. In dozens of ways, Henry Jackson served those goals.

In the process, Scoop Jackson remained unpretentious and good-humored. He lived modestly and always gave his outside earnings to charity. He was one of the few public officials in the 1970s to send his children to D.C. public schools. A Senate insider, he took on his colleagues and got them to limit their outside earnings. He leaves behind an example of honorable and effective public service, responsive to events but informed by conviction and steadiness of purpose.