But the most important activity of man, which leads to eternal life and happiness, is the knowledge of God. This knowledge cannot be attained at once. It must be preceded by a study of one's own soul and of the natural sciences. Through a knowledge of oneself and nature, one arrives finally at a knowledge of God. The soul, originally a _tabula rasa_, is gradually perfected by the ideas which theoretical speculation acquires. These ideas are identified with the rational soul, and there results the acquired Intellect, which, as absolutely immaterial, is immortal and becomes one with the world soul of which it is a part. During life complete union with the spiritual world is impossible. Even Moses could only see the "rear part" of God. But when one has during life kept as far as possible away from the sensuous and corporeal, then at the time of death, when the soul is separated from the body, he will be completely absorbed in the world soul and possess the knowledge of God.
What was poison to Judah Halevi is meat to Abraham Ibn Daud. We must, he says, investigate the principles of the Jewish religion and seek to harmonize them with true philosophy. And in order to do these things properly a preliminary study of science is necessary. Nowadays all this is neglected and the result is confusion in fundamental principles, for a superficial and literal reading of the Bible leads to contradictory views, not to speak of anthropomorphic conceptions of God which cannot be the truth. Many of our day think that the study of philosophy is injurious. This is because it frequently happens in our time that a person who takes up the study of philosophy neglects religion. In ancient times also this happened in the person of Elisha ben Abuya, known by the name of Aher. Nevertheless science was diligently studied in Rabbinic times. Witness what was said concerning Rabbi Yohanan ben Zakkai, Samuel and the Synhedrin.[221] It cannot be that God meant us to abstain from philosophical study, for many statements in the Bible, such as those relating to freedom of the will, to the nature of God and the divine attributes, to the creation of the world, and so on, are a direct stimulus to such investigation. Surely mental confusion cannot be the purpose God had in mind for us. If he preferred our ignorance he would not have called our attention to these matters at all.[222]