John of St. Thomas (John Poinsot) lived from 1584 to 1644 and was one of the luminaries of the Second Scholasticism, which flourished on the Iberian Peninsula at a time when, on the continent, Thomism was virtually eclipsed. This translation of John of St. Thomas's Introduction as it appears in the Solesmes edition makes available to a new generation of students of Thomas a precious handbook and guide to the Summa.