ONE AFTER ANOTHER, like icons in a procession, Thomas Merton books are being published. And read. The recent biography -- The Seven Mountains of Thomas Merton by Michael Mott -- had a surprising but deserving ascent to the best-seller lists. This collection of letters -- the first of four planned volumes -- is another artistic achievement worthy of a rise.

In his 27 years as a priest in the Trappist monastery of Our Lady of Gethsemani in Bardstown, Ky., Merton wrote some 4,000 letters to more than 1,000 correspondents. The Cistercian Order had restrictions on the number of letters a faher or lay brother could write. The limit was four a year. Merton was granted an exemption, one that let him spin off four a day if the spirit and fingers were moving. The recipients had access to Merton's most candid thoughts -- about himself, his religion and his world. Those he wrote to were of a stunning diversity: Reza Arasteh (a Sufi authority, on the mystic Rumi), Erich Fromm, Paul Tillich, Dorothy Day, Ethel Kennedy, Pope John XXIII, Aldous Huxley, Abraham Heschel, W.H. Ferry, Daniel Berrigan and a variety of movers and shakers that in fact included an authority on the real Shakers, who emigrated to the United States in 1774.

Though his letters, Merton seems to have made himself available to anyone interested in a serious trading of ideas. Merton, who wrote Seeds of Contemplation, and then gardened another day with the New Seeds of Contemplation, used his letters for offshoots and new shoots of thoughts found in his books. The editor of this collection, William H. Shannon, believes that because Merton lived in the rural isolation of his monastery and "because he valued friendship so highly, he had no other choice: he had to write letters."

Most of the selections date from the early 1960s up until a short time before Merton's death in Bangkok in December 1968. Nearly all focus on the connections between social issues and the religious experience. Merton spared nothing in getting across the idea of relatedness between ideas, action and belief. In November 1961, he wrote to Pope John XXIII, who was then collecting his thoughts for the 20th century's most important encyclical, Pacem in Terris. "No one of course wants (nuclear) war," he wrote. "But lack of understanding, ignorance, and violence and subtle propaganda -- all conspire together to create a very unsettling mood in the United States. There are many who hate communist Russia with a hatred that implies the desire to destroy this nation (a nation that admittedly poses a threat). But what is worse, the American economy depends more and more on these horrible preparatory measures that move us inevitably toward the greatest disaster. For this reason it is practically impossible to reverse the war machine and disarm. Disarmament could actually ruin many people here. That is why the situation is so grave. Sad to say, American Catholics are among the most war-like, intransigent and violent; indeed, they believe that in acting this way they are being loyal to the Church."

The fire of this kind of talk sent up such smoke from Merton's monastery that the order soon doused it with censorship. It was routine that all of Merton's books had to be approved by Trappist censors, but in 1962, the order went further and quashed his war and peace writings. The hairshirt, however, never became a straitjacket. Merton merely put his thoughts on militarism into his correspondence. The material was mimeographed and issued privately in 1963 as The Cold War Letters.

MERTON'S WRITTEN convictions against war were stronger than his personal ones. That, along with long moods of restlessness and bouts of anger at his treatment by the order, is one of the revelations of this collection. "I am no absolute pacifist," he wrote to Monsignor John Tracy Ellis of Catholic University. Ellis had sent to Merton a denunciatory editorial from the Catholic Standard, the Washington diocesan weekly. "I am in no sense trying to claim that the Church has forbidden war," Merton replied in his own defense against the charge that he had gone too far. To Dorothy Day, he wrote that "It is true that I am not theoretically a pacifist. That only means that I do not hold that a Christian may not fight, and that a war cannot be just."

Merton's letters never explain how he, or anyone else, can be a partial pacifist. He says, in a phrase that has become fashionable in the 1980s, that he is a nuclear pacifist. Everyone claims to be one of those, except that it pushes aside the question of the 40- odd wars now raging throughout the world or the 14,531 wars that a historian has counted in the past 5,500 years.

With Day, Merton tries to have it both ways: "In practice I am with you, except insofar, only, as a policy of totally uncompromising pacifism may tend in effect to defeat itself and yield to one of the other forms of injustice." This was loose talk, and Merton didn't -- and couldn't -- back it up with specifics. Where has pacifism defeated itself? What injustice? What wars have been just?

Merton's vision is sharper when the issues are less defined. He wrote to Reza Arasteh (a scholar now living in Bethesda) and Abdul Aziz on Sufism. Merton read the Koran, cherished Sufi masters like Rumi and Shaikh Ahmad Al-'Alawi. He asked Arasteh to "furnish me with anything from Persian Sufism," a request that Arasteh honored by sending a copy of his own masterwork, Rumi the Persian: Rebirth in Creativity and Love.

Merton was one of several religious leaders in the 1960s who repeatedly called on the church to rouse itself against the violence of war and poverty. Now, 20 years later, large parts of the church are carrying out the vision, only to find well-financed reactionaries seeking to gut such progressive statements as the coming pastoral letter on economics. Merton wrote in a 1941 letter a line that might well serve as the epigraph for the bishops' letter: "The first thing to do is to feed the poor and save the souls of men, and in this sense, feeding the poor means feeding them not by law (which doesn't do a damn bit of good), but first of all at the cost of our own appetites, and with our own hands, and for the love of God. In that case, feeding the poor and saving them are all part of the same thing, the love of our neighbor."

Nearly all of the letters here are expressions of Merton's love -- for ideas and their interplay, for sure, but also for God and for people trying to make sense of creation's mysteries. If you had written to Merton for his views, or to share your own, he would probably have answered with the best prose in his gut and soul.