William of Conches, the twelfth-century Chartrain philosopher, was born at Conches in Normandy at the end of the eleventh century. He probably studied under Bernard of Chartres, learning at least grammar from him, and began teaching in the early 1120s. About 1140 William, who was perhaps now in Paris, had John of Salisbury as one of his pupils; John found him perpetuating the spirit of Bernard's own teaching. However, opposition from less lettered philosophers led William to return to his native Normandy under the protection of Duke Geoffrey Plantagenet, whose son, the future Henry II of England, he taught. He died sometime after 1154.

William left glosses on Priscian in both an early and a later version, and recent evidence suggests that he may have written glosses on Juvenal. However, his other surviving writings testify above all to a considerable achievement in philosophy and in scientific...