The following is from the introduction to a teaching by Thomas Merton called What Is Contemplation? On page 17 of the Renovare book Spiritual Classics edited by Richard Foster and Emilie Griffin we read:

Thomas Merton has perhaps done more than any other twentieth-century figure to make the life of prayer widely known and understood… During his college years he was deeply attracted to Christian belief and became a Roman Catholic (1938) and later a Cistercian (Trappist) monk (1941)… His interest in contemplation led him to investigate prayer forms in Eastern religion. Zen masters from Asia regarded him as the preeminent authority on their kind of prayer in the United States…

Merton’s reputation [is] as a gifted teacher and practitioner of prayer. Do not be concerned as you read the following selection on contemplation, about making precise definitions of “meditation” and “contemplation.” Recognize that different teachers and writers define these terms in different ways… Notice how [Merton] emphasizes the normal, natural quality of contemplative prayer. (Online source)