5. The first clear idea of the nature of the soul came with the philosophically trained thinkers, who were dependent either on Plato, main founder of the doctrine of the immortality of the soul, or on Aristotle, who ascribes immortality only to the creative spirit of God, the supreme Intelligence as a cosmic power. The nearest approach to Plato was Philo,(929) who saw in the three Biblical names for the soul, _nefesh_, _ruah_, and _neshama_, the three souls of the Platonic system,—the sensuous soul, which has its seat in the abdomen; the courageous or emotional soul, situated in the breast; and the intellectual soul, which dwells in the brain and contains the imperishable divine nature. This last is kept in its physical environment as in a prison or a grave, and ever yearns for liberation and reunion with God. The soul of the righteous enters the world of angels after death; that of the wicked the world of demons. Saadia, who was under the influence of Aristotle interpreted from the neo-Platonic viewpoint, did not share the Platonic dualism of matter and spirit, nor did he divide the soul into three parts, seated in various parts of the human body. He finds the soul to be a spiritual substance created simultaneously with the body, and uniting the three forces of the soul distinguished in Scripture into one inseparable whole, the seat of which is in the heart,—wherefore soul and heart are often synonymous in the Bible. This indivisible substance possesses a luminous nature like that of the spheres, but is simpler, finer, and purer than they, and endowed with the power of thought. It was created by God out of the primal ether from which He made the angels, simultaneously with the body and within it. By this union it was qualified to display that moral activity prescribed for it in the divine teaching, the neglect of which would defile and tarnish it. According to Saadia some kind of material substance adheres to the soul as well as to the angels, and on that account he does not hesitate to accept the Talmudic expressions about the abode of the soul after death, or the last judgment which is to take place as soon as the appointed number of souls shall have made their entrance into their earthly bodies, when the souls of the righteous will have their angelic nature recognized, and those of the wicked will have their lower character revealed. However, Saadia combats with so much greater fervor the Hindu teaching of metempsychosis, which had been adopted by Plato and Pythagoras.(930) Bahya connects his theory with the three souls of Plato, and likewise ascribes to the soul an ethereal essence.(931) He holds that its destiny is to raise itself to the order of the angels through self-purification, and finally to return to God as the divine Source of light. To this end the intellectual soul, which has its being from the primal light, must overcome the lower sensuous soul which leads to sin.