Estadista, militar y profesor. Cursó sus primeros estudios en el colegio del Monasterio de São Bento. En 1858 estudió para ingeniero militar en la Escuela Militar de Río de Janeiro, donde los estudios eran gratuitos, y en 1860 se doctoró en Matemáticas y Ciencias Físicas en la Escuela Central. Consiguió alternar estos estudios con la docencia, que comenzó a ejercer en la propia Escuela Militar y en otros colegios, en los que enseñó Matemáticas de nivel superior. En la Guerra de Paraguay , donde luchó en primera línea, contrajo la malaria, enfremedad que le fue consumiendo poco a poco, hasta que murió dolorosamente a los 55 años. Sus principales obras son <i>Memórias sobre a teoria das quantidades negativas</i> (1868) y <i>Relatório sobre a organização do Ensino dos Cegos.</i>
Abstract from English Wikipedia: <blockquote>"Benjamin Constant Botelho de Magalhães (18 October 1836 - 22 January 1891) was a Brazilian military man and political thinker. Primarily a positivist, influenced heavily by Auguste Comte, he was the founder of the positivist movement in Brazil (Sociedade Positivista do Brasil, Brazilian Positivist Society), and later this led to his republican views. He left the Brazilian Positivist society because of internal disagreements, but remained an ardent pupil of Comte until the end of his life. Benjamin Constant was born in Niterói. He had a difficult childhood and attempted suicide at the age of 12. He served in the Paraguayan War, and had a large family. He felt underpaid and unhappy as a soldier. An intellectual at heart, he was a great supporter of Comte's Religion of Humanity. His Republican views led him to found the Clube Militar (or Military Club), with Deodoro da Fonseca, in May 1887. It was based in the Praia Vermelha Military School, and, shortly before his death, overthrew the emperor Pedro II and helped establish a republic. The Brazilian town of Benjamin Constant, near the Amazon river and the Peruvian border, was named after him. He was considered the founder of the Republic in the Constitution of 1891, having died earlier the same year in Rio de Janeiro, aged 54."</blockquote>