The aim of all philosophical theory is the practical realization of moral ideals. Such ideals Judaism presents. None of his predecessors had so definitely and clearly expressed this important thought. Morality produces positive virtues, a healthy family life, and based upon this, a sound constitution of the state. According to this view, all the religious duties of Judaism may be divided into five classes. The first class inculcates the true knowledge and the love of the One God and a purified belief in Him. The second class treats especially of justice and conscientiousness, the chief of all virtues, of forgiveness, kindness, and the love of enemies, all of which have their origin in humility. The third class of precepts treats of the relation of the head of the family to his wife, children, and servants, according to the principles of right and affection. The fourth division, which comprises a large group, prescribes the relation of the citizen to the state and to his fellow-citizens; it inculcates the necessity of loving one's neighbor, of honesty in commerce, and care for the weak and suffering. There is, finally, a fifth class of laws, such as the sacrificial and dietary laws (laws of the ritual), whose purpose is not easily comprehended. These five groups of duties are not equal in importance, faith taking the highest position and the ceremonial laws the lowest, and therefore the prophets also often gave greater prominence to the former. Starting from different premises, Ibn-Daud arrived at a conclusion differing from that of Jehuda Halevi. According to the latter, the pure ritual ordinances constitute the essence of Judaism, whereby the prophetic nature of man is to be kept alive, but for Ibn-Daud they are only of second-rate importance.