The conquerors had found a champion in Doctor Juan Ginés Sepúlveda, who contended that it was lawful to make war on the natives and enslave them in order to promote their conversion and prevent human sacrifices. Las Casas presented thirty propositions in refutation of this view in which he maintained that over a nation whose only sin was idolatry no authority could be justly exercised save by peaceful conversion. Though this was clearly a condemnation of the policy of Spain in the New World, the sincerity of Las Casas and the justice of his cause prevented the king from taking offence at his boldness, and induced him to permit the unrestricted publication of his works while those of his opponent were forbidden to be printed. Henceforth he continued to be consulted on all questions of importance concerning the Indians, his time being devoted mainly to the writing of his history. In 1555 Philip, who had lately ascended the throne, and was then in England, proposed to sell the right of the crown to the reversion of the encomiendas. Las Casas, ever on the alert, saw that this meant perpetual slavery, and determined to exert all his powers to prevent the measure. Through the king's confessor, who had written to him on the subject,[XIX‑22] he made a bold and earnest appeal to the royal conscience. The appeal was not in vain, and he thus paved the way for the final emancipation of the natives. [Sidenote: DEATH OF LAS CASAS.] His last service to the New World was his representation to the council of the Indies of the great inconvenience and prejudice caused to the settlers and natives of Guatemala by the removal to Panamá of the audiencia of the Confines. In 1569, partly owing to his influence, the audiencia was reëstablished in Guatemala. He did not live to see this accomplished, however, for falling ill at Madrid, he died in July 1566, in his ninety-second year. He was buried with becoming honors in the convent chapel of Our Lady of Atocha.