Another birthday has slid by — Ronald Reagan would have been 96 on February 6. Recent books on Reagan and his reign were not designed to celebrate the occasion, but one in particular cannot be read other than as celebrating Reagan.

How? Remarking what?

A professor at the Graduate Center of the City University of New York, John Diggins, has written many books, including one that celebrates the achievements of the American left. Mr. Diggins is not, in other words, a member of the Reagan camp; rather, a historian who surprises by his imagination and fluent capacity to integrate the figure he is looking at into the folds of distinctly American traditions.

In “Ronald Reagan: Fate, Freedom, and the Making of History,” Mr. Diggins identifies Reagan as an Emersonian: that is, as following in the tradition of the Transcendentalist of pre–Civil War days who preached the doctrine of human freedom and self-fulfillment as the fruit of our likeness to God.

Mr. Diggins believes that Reagan was most remarkable for his optimism. When Reagan declared, in 1984, that it was “morning in America,” he was exactly living out his mandate as an Emersonian, greeting each day with the joy that is natural on reminding oneself that God, no less, created you and that you serve him by expressing the joy in every morning as you absorb, and even reflect, divine generosity.

Mr. Diggins lobs a good-sized bomb into the ranks of the routine detractors of Reagan (“an amiable dunce” was Clark Clifford’s contribution to the Reagan portrait). Mr. Diggins paints with a very broad brush. Reagan “may be, after Lincoln, one of the two or three truly great presidents in American history.” This, he explains, is because “Reagan was one of the three great liberators in American history.”

Abraham Lincoln helped emancipate blacks from slavery; Franklin Roosevelt helped wrest Western Europe from fascism; Ronald Reagan helped liberate Eastern Europe from communism.

One aspect of this ground-breaking book reminds me of a personal encounter with General Colin Powell 15 years ago. We were at one side of a social gathering and touched down on modern warfare. He said to me, “Of all the persons I have worked for or alongside, one stands out for his utter hatred of the nuclear bomb, and that is Ronald Reagan.”

Mr. Diggins plows this theme deeply. He tells us that the doctrine of mutual assured destruction, on which our defense policy rested for 40 years, could not engage Reagan’s mind because his imagination declined to accept the postulate of cities and peoples held hostage by the prospect of annihilation.

Some of us, while accepting the generality that Reagan treated nuclear bombs with the correct balance of horror and appreciation, continue to believe that his contingent disposition to use them for certain purposes made strategic peace talks possible. What Reagan could not have done is treat the deployment of nuclear weapons as nothing more than the mechanistic next step in a war progressing neatly up the rungs of firepower, in the manner of a regimental commander calling for more artillery.

Mr. Diggins says that a complementary book should be written giving Mikhail Gorbachev his share of the credit for participating, with Reagan, in this heady dance of survival. No question, such a book is needed.

But in the meantime, one needs to guard against a happy infusion of Emersonian sunniness into such problems as we confront in other parts of the world.

It was a wonderful irony of history when, early last week, American representatives in Europe assured Russia that the reason for our freshly installed anti-missile inventory has nothing to do with any feelings we have about a potential threat from Russia — that our machinery is to guard against Iran. And when Iran is no longer a threat?