We now take it for granted that aspects of the monastic life can sustain our daily lives in the world, but we owe this understanding to John Main, whose vision of a ''monastery without walls'' has grown into a worldwide network of people who today practice Christian meditation. This is his classic book on how to practice contemplative prayer, or Christian meditation. Stepping aside from the busyness of our daily lives and being still in the presence of God is the key to discovering our true selves and knowing God as ''the ground of our being''.