THE APPRECIATIONS of Abe Fortas come with no small degree of agonizing, from the legal peers he so dazzled to the admirers he did deeply disappoint. But there should be no denying that the legacy of Mr. Fortas, who died late Monday at the age of 71, is replete with significant contributions to the history of civil liberties and civil rights in this country--moments of great distinction in his service to the public both as a lawyer and as a Supreme Court justice.

It was these very strengths--of the lawyer, the scholar, the teacher and the champion of liberties-- that made so distressing to so many the nevertheless necessary resignation of Mr. Fortas from the court when improprieties involving outside fees became public.

Mr. Fortas combined a formidable reputation and highly successful practice in the corporate world with a deep attachment to various unpopular causes that challenged his sense of justice. At no time was this more evident or outstanding than before and during the McCarthy era--when Mr. Fortas was never afraid to raise a strong voice against all who were so viciously determined to destroy individual civil liberties.

The small but brave group of outspoken defenders against these purges attests to this day to the courageous leadership of Abe Fortas and his partners in Arnold, Fortas and Porter. "There were no people in town any stronger than those three," a veteran of the battles recalled yesterday, "and nobody stood as high as Abe" for civil freedom and against secret informers, presumptions of guilt and the ravaging of due process.

Later Mr. Fortas argued and won two cases that became judicial landmarks: Durham, which did much to make the legal concept of mental illness more compatible with modern views of medicine and Gideon, in which Mr. Fortas' powerful brief led the Supreme Court to reverse its previous position and rule that states must provide counsel for indigents under criminal charges.

It was this brilliant record that gave every reason to believe that he would serve the Supreme Court with distinction--and which should have prevailed over a vicious and shabby Senate inquisition that finally wound up in the withdrawal of Mr. Fortas' nomination to be chief justice. Still, the record would be squandered--and this lawyer of superior ability, man of privacy, impassioned lover of music and art and other fine things, would return to private practice.

Today, on the bench of the high court and among the many whose rights he defended so staunchly, there is understandable sadness at the loss of an exceptional colleague and a great friend.