An important distinction, however is drawn between
association with other movements and actual membership. In general Bahá'ís are
encouraged to collaborate with all others who are working towards the same
goals as the Faith. Bahá'ís are not permitted, however, to be members of
certain secret societies, of the religious organizations of other Faiths, of
political organizations or, of course, of organizations whose goals are in
conflict with the Bahá'í principles. For example, Bahá'ís would gladly work
together with Christians in humanitarian activities, but a Bahá'í, believing in
Bahá'u'lláh, cannot be a member of a Christian church which believes that
Christ has not yet returned.
(From a letter dated February 14, 1993 written on behalf
of the Universal House of Justice to an individual believer)