A religious community is at least partially defined by the consensus among its members on certain habits of language usage. However, consensus across communities is harder to come by when habits of usage diverge – as they always do when communities are defining themselves by those habits.
The various uses of the word ‘religion’ itself will serve as an example. William James in his Varieties of Religious Experience (1902, 36) defined it ‘arbitrarily’ as ‘the feelings, acts, and experiences of individual men in their solitude, so far as they apprehend themselves to stand in relation to whatever they may consider the divine.’ It would indeed seem arbitrary to rule out anything that people do together as being ‘religious,’ given that public ceremonies and shared beliefs play such a major part in what we commonly call ‘religion.’ But James is no doubt reflecting the Protestant milieu in which he was operating, where the social institutions and collective practices associated with ‘religion’ are supposed to be derived from individual religious experience, and not the other way round.
Walpola Rahula, on the other hand, uses the term ‘religious’ precisely for those communal beliefs and ceremonies which are marginal to the Buddhist ‘Path’:
… the Path … is a way of life to be followed, practised and developed by each individual. It is self-discipline in body, word and mind, self-development and self-purification. It has nothing to do with belief, prayer, worship or ceremony. In that sense, it has nothing which may popularly be called ‘religious.’ … In Buddhist countries there are simple and beautiful customs and ceremonies on religious occasions. They have little to do with the real Path. But they have their value in satisfying certain religious emotions and the needs of those who are less advanced, and helping them gradually along the Path.
— Rahula (1974, 49-50)
Rahula also (like most Buddhist writers) has little use for the concept of ‘the divine’ which is central to theistic religion. But when people say (as many do) that the Buddha Way is not a religion, it is the ‘popular’ rather than the Jamesian individualist concept they are referring to. Other writers (including Peirce) would reject an individualistic religion as oxymoronic; and some Buddhist writers have no problem with calling Buddhist practice ‘religious.’
As for the usage in this book, it assumes that there is no religion without a community – but since there is no selfhood without community either, there is no problem with referring to some ‘feelings, acts, and experiences of individual men’ as religious.