A breathtaking look at some 20th-century giants; Personal Impressions, by Isaiah Berlin. New York: The Viking Press $12.95.

Are an Oxford don's tributes to colleagues, fellow Zionists, literary figures , and world leaders fare for intellectuals only? I hope not. It would be a pity if readers who are unacquainted with Isaiah Berlin's elegant prose, intellectual brilliance, and talent for delineating the elusive mental qualities we call character were to overlook "Personal Impressions."

Undoubtedly those who are absorbed in the life of the mind will relish this fourth and last in the series of collected essays by Sir Isaiah, the Latvian-born, English-bred scholar who is known predominantly on this side of the Atlantic for his books on Russian thinkers and the Enlightenment.

But others who care about the effect of character on the spirit and events of our times will also enjoy this book. It makes a persuasive case for Berlin's conviction that "to know -- to enjoy the friendship of -- a great man must permanently transform one's ideas of what human beings can be or do."

Under Berlin's lens, the fiber of the intellect and the human spirit becomes a thing of wonder -- more breathtakingly alive than in the work of any other writer in recent memory. Whether the subjects are world-renowned or obscure, his comments on them are cosistently stimulating.

Consider, for example, Sir Isaiah's snapshot of moral courage, captured in a 1956 encounter with Boris Pasternak. The Russian poet's single- minded commitment to his vision built a wall of granite around him as solid as the Urals, which could withstand not only authoritarian assaults but also the unwitting lances of those closest to him.

For his safety, Pasternak's friends and relatives had urged him not to defy Communist Party dictums by publishing his final masterpiece, "Doctor Zhivago." When, at the request of the poet's wife, Berlin asked Pasternak if he had considered the consequences of his defiance, the question struck off sparks. Pasternak, writes Berlin, "told me . . . I was worse than that Commonwealth diplomat 11 years ago who had tried to convert him to communism; he had spoken to his son; they were prepared to suffer; i was not to mention the matter again -- I had read the book, I surely realised what it, above all its dissemination, meant to him. I was shamed into silence." (And, yes, the book was published during the poet's lifetime.)

The quality of inspired leadership is illuminated in Berlin's portrait of Sir Winston Churchill. The prime minister's magic lay in his capacity to discen, rouse, and mobilize the heroic impulses latent in human nature, writes Berlin, and to do so without exploiting them for personal or demagogic purposes.

The "sheer intensity" of Churchill's eloquence, Berlin continues, made it seem "he was indeed speaking what was in their hearts and minds. Doubtless it was there; but largely dormant until he had awoken it within them." The prime minister "transformed cowards into brave men, and so fulfilled the purpose of shining armour."

Genius is another quality Berlin praises in his subjects. Often, he says, it has an innoncence about it, which "sees through its own eyes, not those of the spectacles provided by conventional wisdom or some uncriticized dogma."

It was Einstein's innocence, Berlin continues, that "caused him to reject the accepted notions of physical spacetime and boldly offer the hypothesis of gravitational waves and light quanta against the resistance of physicists and philosophers. . . ."

It was Nijinsky's innocence that allowed the renowned Russian ballet dancer to accomplish the impossible. When asked how he managed to leap so high, Nijinsky "saw no great problem in this," Berlin writes. "Most people, when they leapt in the air, came down at once; 'Why should you come down immediately? Stay in the air a little before you return, why not?' [Nijinsky] is reported to have said."

Berlin also lauds vitality, generosity, lack of pretension, integrity, and nobility wherever he finds them.His words of praise for Felix Frankfurter could apply equally to himself: He "liked whatever could be liked, omnivorously, and he greatly disliked having to dislike."

Others in this volume: Franklin Roosevelt (whom Berlin knew only by reputation); poet Anna Ahkmatova (included in a never-before published chapter on Russian writers); novelist Aldous Huxley; Zionist leader Chaim Weizmann; Auberon Herbert; historian and Zionist supporter Lewis Namier; and Oxford scholars Richard Pares, Hubert Henderson, J. L. Austin, John Petrov Plamenatz, and Maurice Bowra.

Berlin's impressions are utterly personal and thus open wide to differences of opinion; one suspects they reveal as much about Sir Isaiah as his subjects.In fact, the most tantalizing portrait, the most vivid, the figure a reader would most like to meet is Isaiah Berlin himself.