NAIN, LEWIS SEBASTIAN DE, a French critic and historian, was the son of a master of the requests, and was born at Paris in 1637. At ten years old he went to school at Port Royal, and became one of the best writers of that institution. Sacy, his intimate friend and counsellor, prevailed with him in 1676 to receive the priesthood; which it seems, his great humility would not before suffer him to aspire to. This virtue he seems to have possessed in the extreme; so that Bossuet, seeing one of his letters to Father Dami, with whom he had some little dispute, besought him merily "not to be always upon his knees before his adversary, but raise himself up now and then." He was solicited to push himself forward in the church, and Buzanval, bishop of Beauvois, wished to have him for his successor; but Nain, regardless of dignities, wished for nothing but retirement, so that he might indulge in the mortifications of a religious life and the indefatigable cultivation of letters. He died in 1698, aged 61. His principal works are, 1. Memoirs on the ecclesiastical history of the six first ages of the church, 16 vols. 4to. 2. The history of the emperors, 6 vols. 4to. These works are deduced from original sources, and composed with the utmost fidelity and accuracy.