We have now gone through Bahya's philosophical chapter giving us the metaphysical basis of his ethico-religious views. That his purpose is practical and not theoretical is clear from his definition of what he calls the "acknowledgment of the unity of God with full heart," not to speak of the title of the book itself, the meaning of which we explained at the beginning of this section, and the nine chapters in Bahya's work following upon the first, which constitute its real essence and purpose. To acknowledge the unity of God with full heart means, he tells us, that one must first know how to prove the existence and unity of God, to distinguish God's unity from every other, and then to make his heart and his tongue unite in this conception.[120] It is not a matter of the intellect merely, but of the heart as affecting one's practical conduct. The adequacy of the conception is destroyed not merely by thinking of God as multiple, or by worshiping images, sun, moon and stars; it is made null and void likewise by hypocrisy and pretence, as when one affects piety before others to gain their favor or acquire a reputation. The same disastrous result is brought about by indulging the low physical appetites. Here the worship of the appetites is brought into competition and rivalry with devotion to the one God.[121] Our object being to trace the philosophical conceptions in mediæval Jewish literature, we cannot linger long in the study of the rest of Bahya's masterpiece, which is homiletical and practical rather than theoretic, and must content ourselves with a very brief résumé of its principal contents. In studying the nature and attributes of God we reached the conclusion that while a knowledge of him is absolutely necessary for a proper mode of life, we cannot form an idea of him as he is in himself, and are left to such evidence as we can gather from the world of which he is the author. It becomes our duty, therefore, to study nature, as a whole and in its parts, conscientiously and minutely, in order to realize clearly the goodness and wisdom of God as exhibited therein. For various reasons we are apt to neglect this study and miss the insight and benefits arising therefrom. Chief among these hindering circumstances are our excessive occupations with the pleasures of this world, and the accidents and misfortunes to which mortal is heir, which blind him to his real good, and prevent him from seeing the blessing in disguise lurking in these very misfortunes. But it is clear that man has a duty to study the divine goodness and wisdom as exhibited in nature, else of what use is his faculty of reason and intelligence, which raises him above the beast. If he neglects it, he places himself below the latter, which realizes all the functions of which it is capable. Bible and Talmud are equally emphatic in urging us to study the wonders of nature.