Vatican II speeaks of the Eucharist as the source and summit of the Christian life (Lumen Gentium 11). Our teachers and guides for these insightful reflections on this great mystery of our faith are six great Doctors of the Church: St. Catherine of Siena, St. Teresa of Avila, St. John of the Cross, St. Francis de Sales, St. Alphonsus de Liguori, and St. Therese of Lisieux. Biographical, historical, and doctrinal material is incorporated into each chapter insofar as it can assist us in understanding the message of that particular Doctor.