Letters to Malcolm: Chiefly on Prayer is a book by C. S. Lewis, published posthumously in 1964. The book takes the form of a series of letters to a fictional friend, "Malcolm", in which Lewis meditates on prayer as an intimate dialogue between man and God. Beginning with a discussion of "corporate prayer" and the liturgical service, Lewis goes on to consider practical and metaphysical aspects of private prayer, such as when to pray and where, ready-made prayer, petitionary prayer, prayer as worship, penitential prayer, and prayer for the dead. The concluding letter discusses "liberal" Christians, the soul and resurrection.