Contemporaneous writers describe John as a man of wit who was very keen on concentrating power on himself, but at the same time possessed a benevolent and kind demeanor. His youthful education as master of a religious order made him an unusually learned king for the Middle Ages. His love for knowledge and culture was passed on to his sons, who are often referred to collectively by Portuguese historians as the "illustrious generation" ("Ínclita Geração"): Edward, the future king, was a poet and a writer; Peter, the Duke of Coimbra, was one of the most learned princes of his time; and Prince Henry the Navigator, the duke of Viseu, invested heavily in science and the development of nautical pursuits. In 1430, John's only surviving daughter, Isabella, married Philip the Good, Duke of Burgundy, and enjoyed an extremely refined court culture in his lands; she was the mother of Charles the Bold.