world, and how to defend these matters before an unbeliever. Then if he has time left, he may devote it to legalistic discussions, and there would be no harm. Self-examination, in order to purify oneself from vices great and small, represents the second stage of getting on the road and travelling from station to station. The final stage, arriving in the holy city and celebrating there, is to have a perfect knowledge of God. He who attains this is the best of wise men, having the best of knowledge, which deals with the noblest subject. The reader must not expect to find it all in this book. If he reads this and does not study the subject for himself, he is like a man who spent his time in reading about medicine and cannot cure the simplest ailment. The knowledge of God is a form that is bestowed from on high upon the rational soul when she is prepared by means of moral perfection and scientific study. The prophet puts all three functions of the soul on the same level, and gives preference to knowledge of God. "Thus saith the Lord," says Jeremiah (9, 22), "Let not the wise man glory in his wisdom [rational soul], neither let the mighty man glory in his might [spirited soul], let not the rich man glory in his riches [nutritive soul]: but let him that glorieth glory in this, that he understandeth, and knoweth me...." Jeremiah also recommends (_ib._) knowing God through his deeds--"That I am the Lord which exercise loving-kindness"--in order that man may imitate him.[231] We have now a general idea of Ibn Daud's attitude and point of view; and in passing to the details of his system it will not be necessary to rehearse all the particulars of his thought, much of it being common to all mediæval writers on Jewish philosophy. We shall confine ourselves to those matters in which Ibn Daud contributed something new, not contained in the writings of his predecessors. Following the Aristotelian system, he begins by describing substance and accident and gives a list and characterization of the ten categories. This he follows up by showing that the classification of the ten categories lies at the basis of the 139th Psalm. It needs not our saying that it must be an extraordinary mode of exegesis that can find such things in such unusual places. But the very strangeness of the phenomenon bears witness to the remarkable influence exerted by the Aristotelian philosophy upon the thinking of the Spanish Jews at that time.[232]