On account of the confusion which arose in the middle ages, as a result of which Neo-Platonic writings and doctrines were attributed to Aristotle, Alfarabi and Avicenna worked out a scheme which combined the motion theory of Aristotle with the doctrine of emanation of Plotinus. The theory is based upon a principle alleged to be Aristotle's that from a unitary cause nothing but a unitary effect can follow. Hence, said Avicenna, God cannot have produced directly all the world we see in its complexity. He is the direct cause of the first Intelligence only, or first angel as Judah Halevi calls him. This Intelligence contemplates itself and it contemplates its cause. The effect of the latter act is the emanation of a second intelligence or angel; the effect of the former is a sphere--that of the fixed stars, of which the first Intelligence is the mover. The second Intelligence again produces a third Intelligence by its contemplation of the First Cause, and by its self-contemplation it creates the second sphere, the sphere of Saturn, which is moved by it. So the process continues until we reach the sphere of the moon, which is the last of the celestial spheres, and the Active Intellect, the last of the Intelligences, having in charge the sublunar world. This fanciful and purely mythological scheme arouses the antagonism of Judah Halevi. It is all pure conjecture, he says, and there is not an iota of proof in it. People believe it and think it is convincing, simply because it bears the name of a Greek philosopher. As a matter of fact this theory is less plausible than those of the "Sefer Yezirah"; and there is no agreement even among the philosophers themselves except for those who are the followers of the same Greek authority, Empedocles, or Pythagoras, or Aristotle, or Plato. These agree not because the proofs are convincing, but simply because they are members of a given sect or school. The objections to the theory just outlined are manifold. In the first place why should the series of emanations stop with the moon? Is it because the power of the First Cause has given out? Besides why should self-contemplation result in a sphere and contemplation of the First Cause in an Intelligence or angel? It should follow that when Aristotle contemplates himself he produces a sphere, and when he contemplates the First Cause he gives rise to an angel. Granting the truth of the process, one does not see why the mover of Saturn should not produce two more emanations, one by contemplating the Intelligence immediately above it, and the other by contemplating the first Intelligence, thus making four emanations instead of two.[207] In his outline of the philosophers' psychology, which as we have seen (p. 175) is borrowed verbally from Avicenna, what is new to us is the exposition of the inner senses and the account of the rational faculty. We must therefore reproduce it here in outline together with Judah Halevi's criticism.