Yet, though withdrawn to his Dominican convent, he did not pass his hours in slothful seclusion. He again appeared as the champion of Indian freedom in the famous controversy with Sepulveda, one of the most acute scholars of the time, and far surpassing Las Casas in elegance and correctness of composition. But the Bishop of Chiapa was his superior in argument, at least in this discussion, where he had right and reason on his side. In his “Thirty Propositions,” as they are called, in which he sums up the several points of his case, he maintains that the circumstance of infidelity in religion cannot deprive a nation of its political rights; that the Holy See, in its grant of the New World to the Catholic sovereigns, designed only to confer the right of converting its inhabitants to Christianity, and of thus winning a peaceful authority over them, and that no authority could be valid which rested on other foundations. This was striking at the root of the colonial empire as assumed by Castile. But the disinterested views of Las Casas, the respect entertained for his principles, and the general conviction, it may be, of the force of his arguments, prevented the court from taking umbrage at their import, or from pressing them to their legitimate conclusion. While the writings of his adversary were interdicted from publication, he had the satisfaction to see his own printed and circulated in every quarter. From this period his time was distributed among his religious duties, his studies, and the composition of his works, especially his History. His constitution, naturally excellent, had been strengthened by a life of temperance and toil; and he retained his faculties unimpaired to the last. He died after a short illness, July, 1566, at the great age of ninety-two, in his monastery of Atocha, at Madrid.