Samuel Ibn-Nagrela, and the disputes that arose ended in bitter personalities. The two chief exponents of the Jewish culture of this period, the noble-minded prince and the master of the Hebrew language, thus became bitter, irreconcilable enemies. Feeling the approach of old age, which with Plato he calls "the mother of forgetfulness," Ibn-Janach devoted himself to his greatest work, wherein he summed up his researches, and deposited the treasures of his soul life. Ibn-Janach was not only the creator of the science of Hebrew syntax, but he also developed it almost to perfection. None before him, and but few since his time, have entered into all the niceties of the holy language with so much discrimination as Ibn-Janach. He first drew attention to the ellipses, and to the misplacement of letters and verses in the Holy Scriptures, and he was sufficiently daring to explain that various dark and apparently inexplicable expressions were due to the change of a letter or a syllable. He explained over two hundred obscure passages by means of the supposition that the writer had substituted an inappropriate word for a more fitting one. By the insertion of the correct word, Ibn-Janach often gives the intended meaning to a number of verses which up to his time had been interpreted in a childish way. He was the first rational Bible critic. Although convinced of the divinity of Holy Writ, he did not, like others, rate the language so highly as to accept sheer nonsense; but he assumed that, even though inspired, words addressed to mankind must be interpreted according to the rules of human language. Ibn-Janach did not, indeed, assert that the copyists and punctuators had altered or corrupted the holy literature from want of understanding, but that being human they had erred. He justly called his chief work (which with five others he wrote in Arabic) "Critique" (Al Tanchik), and divided it into two parts--into grammar with exegesis ("Al-Luma', Rikmah"), and lexicon ("Kitab Al-Assval").