It is futile to maintain that the history of Arabic philosophy shows a lack of originality in the Semitic mind; for one thing not one of the philosophers of first rank after al-Kindi was of Arab birth, very few could be described as Semitic. It would be more correct to say that the Greek philosophers stood alone, until quite modern times, in attempting anything which could be described as a scientific psychology. Until the methods and material of modern natural science came to be applied to psychological research there was little, if any, advance on the psychological theories of the ancient Greek investigators, and the only point of difference in later schools was as to which particular aspect of ancient research would be selected as the starting-place. Here lies the great importance of al-Kindi, for it was he who selected and indicated the starting-point which all the later Arabic philosophers began from, and selected the material which they developed. The particular basis thus selected by al-Kindi was the psychology of Aristotle’s _de Anima_ as expounded by Alexander of Aphrodisias. This was suggested but not in all respects clearly indicated by the Syriac philosophers, and it seems certain that al-Kindi’s development was very largely influenced by the _Theology of Aristotle_, a work which he evidently esteemed very greatly. The relation between Alexander Aphr. and Plotinus, whose teaching appeared in the _Theology_, may be described as being that Alexander’s teaching contained all the germs of neo-Platonism, whilst Plotinus shows the neo-Platonic system fully worked out. As first presented this system must have seemed fully consistent with the teaching of the Qur´an, indeed it would appear as complementary to it. In man was an animal soul which he shared with the lower creation, but added to it was a rational soul or spirit which proceeded directly from God and was immortal because it was not dependent on the body. The possible conclusions which proved to be inconsistent with the teachings of revelation were not as yet fully worked out.