But the grandest fruit of his genius is undoubtedly his Apology. The address to the king is dated Nov. 25th, 1675; the Latin edition is dated Amsterdam, 1676. He was therefore only twenty-seven years of age when his masterpiece was completed; and as it was first published, so it stands to-day, unaltered. His genius matured early, though to the great perplexity of our human judgment, early maturity was followed by early death. For three or four years, his English brethren had been struggling with an unusually strong tide of misrepresentation and obloquy. He could not be a passive looker-on now that God had given him rest from persecution. He would endeavour to state the opinions of his brethren, and the rationale of them, with a fulness for which they had neither time nor opportunity. It was a brotherly and chivalrous feeling, and it had its own reward. The work was at once accepted as a standard exposition of Quakerism. It has been profusely eulogised by many who have not accepted the creed it defends. Even Voltaire has warmly praised its pure Latinity. He called it "the finest Church Latin that he knew." Sir James Mackintosh in his "Revolution in England," calls it "a masterpiece of ingenious reasoning, and a model of argumentative composition, which extorted praise from Bayle, one of the most acute and least fanatical of men." The writer in the "Theological Review," from whom we have already quoted, is enthusiastic in his admiration of it. After speaking of Rutherford's "Letters," and Scougal's "Life of God in the Soul of Man," he proceeds, "Greater, where they were greatest, than Rutherford or Scougal, was Robert Barclay; it is a country's loss that his splendid Apologia should be left in the hands of a sect. Here, indeed, is a genuine outcome of the inner depth of the nation's worship; something characteristic and her own; a gift to her religious life akin to her profoundest requirements; and if she did but know it, far worthier of the acceptance of her people than any religious aid which she has ever welcomed from the other side of the border; more satisfying to the intellect than the close scholastic conclusions of the English divines at Westminster; more full of melody to the soul than even the rude music of those ballad psalms which the Kirk had not been too proud to adapt from the version of the Cornish statesman. One great original theologian, and only one, has Scotland produced; he it is the history of whose life and mind we shall endeavour to approach in the present Article." Theol. Review, 1874, p. 528.