After Philip III's older brother Don Carlos died insane, Philip II had concluded that one of the causes of Carlos' condition had been the influence of the warring factions at the Spanish court. He believed that Carlos' education and upbringing had been badly affected by this, resulting in his lunacy and disobedience, and accordingly he set out to pay much greater attention to arrangements for his later sons. Philip II appointed Juan de Zúñiga, then Prince Diego's governor, to continue this role for Philip, and chose García de Loaysa as his tutor. They were joined by Cristóbal de Moura, a close supporter of Philip II. In combination, Philip believed, they would provide a consistent, stable upbringing for Prince Philip, and ensure he avoided the same fate as Carlos. Philip's education was to follow the model for royal princes laid down by Father Juan de Mariana, focusing on the imposition of restraints and encouragement to form the personality of the individual at an early age, aiming to deliver a king who was neither tyrannical nor excessively under the influence of his courtiers.
Philip III of Spain, 1599-1601, The Phoebus Foundation
Prince Philip appears to have been generally liked by his contemporaries: 'dynamic, good-natured and earnest,' suitably pious, having a 'lively body and a peaceful disposition,' albeit with a relatively weak constitution. The comparison with the memory of the disobedient and ultimately insane Carlos was usually a positive one, although some commented that Prince Philip appeared less intelligent and politically competent than his late brother. Indeed, although Philip was educated in Latin, French, Portuguese and astronomy, and appears to have been a competent linguist, recent historians suspect that much of his tutors' focus on Philip's undeniably pleasant, pious and respectful disposition was to avoid reporting that, languages aside, he was not in fact particularly intelligent or academically gifted. Nonetheless, Philip does not appear to have been naive – his correspondence to his daughters shows a distinctive cautious streak in his advice on dealing with court intrigue.
Philip first met the Marquis of Denia – the future Duke of Lerma – then, a gentleman of the King's chamber, in his early teens. Lerma and Philip became close friends, but Lerma was considered unsuitable by the King and Philip's tutors. Lerma was dispatched to Valencia as a Viceroy in 1595, with the aim of removing Philip from his influence; but after Lerma pleaded poor health, he was allowed to return two years later. By now in poor health himself, King Philip II was becoming increasingly concerned over the prince's future, and he attempted to establish de Moura as a future, trusted advisor to his son, reinforcing de Loaysa's position by appointing him archbishop. The prince received a new, conservative Dominican confessor. The following year, Philip II died after a painful illness, leaving the Spanish Empire to his son (and grandnephew), King Philip III.