He rapidly came under the influence of Charles E O Carter who guided Addey's explorations in both philosophy and astrology. In philosophy this meant an acknowledgement of the worth of all the great world religions and philosophies, but an especial interest in the Platonic tradition; in astrology Carter (who was for some time the President of the Astrological Lodge of the Theosophical Society) encouraged Addey's mystical leanings. Central to Addey's later work on the Harmonic theory of astrology was the conviction that the mystical and the scientific were not mutually exclusive and that neither was complete without the other.