“Enq: Which system do you prefer or follow, in that case, besides Buddhistic ethics?
Theo: None, and all. We hold to no religion, as to no philosophy in particular; we cull the good we find in each. But here, again, it must be stated that, like all other ancient systems, Theosophy is divided into Exoteric and Esoteric Sections.
Enq: What is the difference?
Theo: The members of the Theosophical Society at large are free to profess whatever religion or philosophy they like, or none if they so prefer, provided they are in sympathy with, and ready to carry out one or more of the three objects of the Association.
The Society is a philanthropic and scientific body for the propagation of the idea of brotherhood on practical instead of theoretical lines.
The Fellows may be Christians or Mussulmen, Jews or Parsees, Buddhists or Brahmins, Spiritualists or Materialists, it does not matter; but every member must be either a philanthropist, or a scholar, a searcher into Aryan and other old literature, or a psychic student.
In short, he has to help, if he can, in the carrying out of at least one of the objects of the programme. Otherwise he has no reason for becoming a “Fellow”.
Such are the majority of the exoteric Society, composed of “attached”, and “unattached” members. These may, or may not, become Theosophists de facto.
An “attached member” means one who has joined some particular branch of the T.S. An “unattached”, one who belongs to the Society at large, has his diploma, from the Headquarters (Adyar, Madras), but is connected with no branch or lodge.
Members they are, by virtue of their having joined the Society; but the latter cannot make a Theosophist of one who has no sense for the divine fitness of things, or of him who understands Theosophy in his own – if the expression may be used – sectarian and egotistic way.
“Handsome is, as handsome does” could be paraphrased in this case and be made to run: “Theosophist is, who Theosophy does.””
H. P. Blavatsky
The Mark Of God: Understanding Your "I AM Presence" 