Next to his impetuous devotion to the true relations of things, the source of Otis's power lay in his adequate preparation for the life of an advocate. Bred to the law at a time long before the pathway had been smoothed by the multiplication of elementary works and other modern improvements, he yet fully mastered that abstruse science, which perhaps does more to quicken and invigorate the understanding than many of the other kinds of learning put together. As a sufficient foundation for his later legal studies he had pursued at Harvard, the foremost college in the colonies, not only the regular undergraduate classical course, but also the three years of work required for the Master's degree. Moreover, in conformity with his views on the necessity of a generous and comprehensive culture of the mind as a means of success at the bar, or in any professional career, Otis did not plunge at once from his collegiate courses into the routine of the legal office; but allowed himself two years of self-directed general study with a view toward further disciplining his mind and widening his information. The subjects thus pursued and the general culture which he acquired served to open and to liberalize his mind in nearly the same proportion as the assiduous study of the law was next to invigorate and quicken it. In conversation with his brother he remarked, "that Blackstone's Commentaries would have saved him seven years' labor pouring over and delving in black letter." He appears to have formed a very correct judgment respecting the nature of professional education and the best means of mastering its abstruse details. He constantly inculcated upon the young men who came to study in his office the maxim, "that a lawyer ought never to be without a volume of natural or public law, or moral philosophy, on his table or in his pocket." After two years of practice in Plymouth, he removed to Boston (1750), where he found the larger field which was demanded by his superior training and abilities; and he very soon rose to the front rank of his profession.