What is religion? The Oxford Dictionaries online (11) gives the primary definition of religion as 'belief in ... a superhuman controlling power, especially a personal God or gods'. Wattis and Curran (12), writing in a health care context, suggested that religion can be seen as a means of relating to God and our fellow human beings, connected with the beliefs and rituals found in many faiths and often associated with power structures; briefly, 'the politics of spirituality'. Some definitions would not necessarily refer to God and would implicitly include a number of systems ('isms') that we don't normally think of as religions (e.g. capitalism, socialism, communism, materialism, economism and even secularism). These may for some people function as a religion; see for example the critique of economism as a 'religion' by Richard Norgaard (13).
Psychologists have developed different ways of understanding religion. Allport (14) made a distinction between mature and immature religion, later conceptualised as intrinsic and extrinsic religion (15). Intrinsic religion is essentially religion that is 'of the heart', also described as 'religion as an end in itself'. Extrinsic religion is seen as 'skin deep', self-serving and essentially a means to an end. Intrinsic religion seems intuitively closer to what we mean by spirituality. Batson et al (16) added a third category to intrinsic and extrinsic religion: 'religion as quest'. This, too, overlaps with ideas about spirituality.