Thus Vico did not feel obliged to write a new treatise on metaphysics. It seemed enough to add a mere post-script to his former work, and to correct to some extent his earlier assertions. His new theory of knowledge, while adhering strictly to the criterion of truth enunciated by him in opposition to that of Descartes--the principle, that is, that only the creator of a thing can know it--divided the whole of reality into the world of nature and the world of man. But, while it laid down that the world of nature is created by God and that therefore God alone knows it, it restricted its agnosticism to this field. It asserted, on the other hand, that the human world, being man's creation, is known by man. In this way it raised the knowledge of human affairs, formerly considered merely approximate and probable, to the rank of perfect science; and it expressed surprise that philosophers should so laboriously endeavour to attain to science of the world of nature, which is a sealed book to mankind, while passing over the world of man, the science of which is attainable. The cause of this error he traced to the ease with which man's mind, involved and buried as it is in the body, feels bodily things, and the labour and pains it costs it to understand itself, as the bodily eye sees all objects outside itself, but in order to see itself requires the help of the mirror. In everything else his system remained unchanged. Beyond the world of man lay the supernatural world, inaccessible to man, and the world of nature, itself also in a sense supernatural. Beyond the perfect knowledge which man could have of himself lay the metaphysic of Christian Platonism, now reduced to impotence, but continuing none the less to embarrass mankind. The natural sciences were now, as before, regarded as incomplete forms of knowledge: mathematics as a system of abstractions, absolutely valid in the abstract but in face of reality powerless. The Aristotelian syllogism, the Stoic sorites, and the Cartesian geometrical method were pursued with the same hatred as before; and the same enthusiastic praise was lavished upon the induction advocated and illustrated in his _Organum_ by Bacon, that "great philosopher and great statesman," and fruitfully employed by his countrymen in experimental philosophy.