The Hidden Ground of Love : THE LETTERS OF THOMAS MERTON ON RELIGIOUS EXPERIENCE AND SOCIAL CONCERNS, selected and edited by William H. Shannon (Farrar, Straus & Giroux: $27.95; 669 pp.)

Since Thomas Merton’s accidental death in 1968, we have seen everything from picture books on people and places dear to him to two lengthy and widely reviewed recent biographies. Sometimes it seems that the ongoing flow of comment about the man, so intriguing as a person, is on the verge of totally eclipsing his work.

Therefore, welcome indeed is this first installment in a projected four-volume series of Merton’s letters, simply because it returns us to the original source--his words.

And the words of these letters, in which Merton addresses himself to what his able editor William H. Shannon labels “religious experience and social concerns” (later volumes will focus on other subjects, such as literature), provide a valuable addition to the Merton oeuvre. Shannon points out that Merton was a natural letter writer. I think it could be argued further that in a way all of his major writing has an epistolary feel. The technique of blending autobiography with instructional commentary in rich, intimate prose--prose that manages to be meanderingly relaxed, yet always able to slip into truly rare and beautiful insight--is the essence of “The Seven Storey Mountain.” That early book documents his own zigzagging path toward spiritual fulfillment as a Trappist monk. A best seller, it made Merton instantly famous in 1948, much to his own and his publisher’s surprise.

Actually, the bulk of this sizable volume is dated well after that tranquil beginning. During the rocky ‘60s, the middle-aged Merton was caught up in an investigation of Eastern religions and deeply involved in the cause of pacifism. It was a time when he was living in a hermit’s cottage on his monastery’s grounds in Kentucky, blue-jean clad and now aware of the confines of the contemplative life of the strict order he had chosen. His vocal complaints about travel restrictions and the straitjacket of censorship of much of his work by superiors are well documented here. It was also a time when, despite those grumblings, he still aired honest affection for his religious vocation and could assume a pretty traditional line when sending an extensive analysis of the vow of obedience to his friend, the poet-priest Daniel Berrigan.

Though the letters to public figures like Jacqueline Kennedy, the mayor of Hiroshima and two popes make interesting historical documents, the real writing comes in correspondence with lesser-knowns. His thoughts on Zen Buddhism and Islam sent to scholars are moving miniature essays in themselves. And his understanding, passionate remarks, peppered with street talk and man as an emphasizer, to those in the peace and civil rights movements show him always in the vanguard--and never at a loss for friendly humor either, as when in exasperation, he refers to Lyndon Johnson as “a well-meaning but inept goof.”

And so often those jewels of wonderful insight in wonderful words. Listen: “. . . the contemplative is not the man who has fiery visions of the cherubim carrying God on their imagined chariot, but simply he who has risked his mind in the desert beyond language and beyond ideas where God is encountered in the nakedness of pure trust. . . . “