The Iranian monotheism is more ethical, while the Indian is more metaphysical in its character. Such a difference in their respective spiritual developments was owing, no doubt, to the more active vigour of life in the old Persians and the contemplative quietude of mind in the Indians.
This is the first confirmation I received that validated my own observations : That Persia was Ethical while India was Metaphysical.
Philosophy integrates both in a beautiful marriage.