Among the peculiar phenomena of religion, and in particular of Judaism, the one that occupies a fundamental position is the revelation of God's will to man and his announcement of the future through prophetic visions. Dreams and divination had already been investigated by Aristotle and explained psychologically. The Arabs made use of this suggestion and endeavored to bring the phenomenon of prophecy under the same head. The Jewish philosophers, with the exception of Judah Halevi and Hasdai Crescas, followed suit. The suggestion that prophecy is a psychological phenomenon related to true dreams is found as early as Isaac Israeli. Judah Halevi mentions it with protest. Abraham Ibn Daud adopts it, and Maimonides gives it its final form in Jewish rationalistic philosophy. Levi ben Gerson discusses the finer details of the process, origin and nature of prophetic visions. In short the generally accepted view is that the Active Intellect is the chief agent in communicating true visions of future events to those worthy of the gift. And to become worthy a combination of innate and acquired powers is necessary together with the grace of God. The faculties chiefly concerned are reason and imagination. Moral excellence is also an indispensable prerequisite in aiding the development of the theoretical powers. Proceeding to the more dogmatic elements of Judaism, Maimonides was the first to reduce the 613 commandments of Rabbinic Judaism to thirteen articles of faith. Hasdai Crescas criticised Maimonides's principle of selection as well as the list of dogmas, which he reduced to six. And Joseph Albo went still further and laid down three fundamental dogmas from which the rest are derived. They are the existence of God, revelation of the Torah and future reward and punishment. The law of Moses is unanimously accepted as divinely revealed. And in opposition to the claims of Christianity and Mohammedanism an endeavor is made to prove by reason as well as the explicit statement of Scripture that a divine law once given is not subject to repeal. The laws are divided into two classes, _rational_ and _traditional_; the former comprising those that the reason approves on purely rational and ethical grounds, while the latter consist of such ceremonial laws as without specific commandment would not be dictated by man's own reason. And in many of these commandments no reason is assigned. Nevertheless an endeavor is made to rationalize these also. Bahya introduced another distinction, viz., the "duties of the heart," as he calls them, in contradistinction to the "duties of the limbs." He lays stress on intention and motive as distinguished from the mere external observance of a duty or commandment.