The writings in which Vico expounds his first theory of knowledge, _De ratione studiorum_ and _De antiquissima Italorum sapientia,_ together with the polemical works bearing upon them, belong to the four years from 1708 to 1712. In the following decade Vico was gradually led to devote himself more and more to research in the history of law and of the State. He read Grotius as a preparation for writing the life of Antonio Carafa, and plunged into the controversy on Natural Rights. He pursued his studies of Roman law and the science of law in general, in order to fit himself for a chair of jurisprudence at Naples University. He pondered upon the origins of languages, religions, and states, out of dissatisfaction with his own historical theories as set forth in the _Be antiquissima_; perhaps also his convictions were shaken by a well-directed criticism by the editor of the _Giornale dei letterati._ His profession, the teaching of rhetoric, gave him continual opportunities for meditating upon the nature and relations of poetry and the forms of language. Thus even if it is inaccurate to say that Vico was led to his later position culminating in the _Scienza Nuova_ by a philological, not a philosophical process (since clearly a philosophical position can only come into being through a process no less philosophical), it is at least certain that the material and stimulus for his new thought were supplied by philological studies. These studies seem to have impressed upon him a fact of great importance; namely, that this subject-matter could only be and had actually been worked over by his thought through the aid of certain necessary principles, appearing on every page of the history which he had chosen for investigation. He had once believed that the moral sciences, as compared with the mathematical method, took the lowest place as regards certainty. But now, in his daily acquaintance with these sciences, he had come to hold the opposite view; namely, that nothing could be firmer than the foundation of the moral sciences! This certainty was not the simple self-evidence of Descartes, in which the object, however internal it is said to be, remains extrinsic to the subject. It was a truly internal certainty, reached by an internal process. In the assimilation of historical facts, Vico felt himself to be making more truly his own something that already belonged to him; to be entering into possession of what was his by right. He was reconstructing the history of man; and what was the history of man but a product of man himself? Is not the creator of history simply man, with his ideas, his passions, his will, and his actions? And is not the mind of man, the creator of history, identical with the mind which is at work in thinking it and knowing it? The truth of the constructive principles of history then comes not from the validity of the clear and distinct idea, but from the indissoluble connexion of the subject and object of knowledge.