Diogo de Sá

Humanist, jurist, theologian, mathematician, and soldier. Diogo de Sá Soutomaior was the son of Fernão de Sá Soutomaior and a cousin of the poet Sá de Miranda and the governor-general of Brazil, Mem de Sá. A warrior nobleman in the service of King John III, he left for India on a yet undetermined date. His presence in the East, where he took part in various military exploits and diplomatic missions, was documented in a recent study by Ana Cristina da Costa Gomes between 1525 and 1546. He is believed to have returned to the Kingdom in 1533, and was referred to as a "master" of mathematics at the Studies of Coimbra in 1538. He embarked for India again in 1541. Upon returning to the Kingdom, he went to Paris where he at least frequented the university environment and published his first two treatises (De Navigatione, 1549 and De Progenitura, 1551). Back in Lisbon, he was granted a coat of arms letter by King Sebastian in 1561, and between 1557 and 1562 he wrote the «Tratado dos Estados Eclesiásticos e Seculares» and «Inquisição e Segredos da Fé», which were not granted printing licenses; the former appeared in the Index of Prohibited Books of 1581. Until the mid-20th century, references to Diogo de Sá were made solely in connection with Pedro Nunes due to his contradiction of two treatises by the famous mathematician («Tratado de Certas Dúvidas da Navegação» and «Tratado em Defensão da Carta de Marear», published together with the Tratado da Esfera in 1537) concerning rhumb lines or loxodromic curves, arguing that mathematics could not explain facts unknown to it. Trained in scholastic Aristotelianism, according to Luís de Albuquerque, Diogo de Sá "was utterly incapable of understanding mathematical abstraction." Pedro Nunes responded to this contradiction with the manuscript «Defensão do tratado de rumação do globo para a arte de navegar» (unpublished until 1952). A man of his time, "a living example of the topos of 'arms and letters'", his multifaceted work reflects the ideological contradictions of 16th-century Portuguese society.