The issue arises about where are the boundaries of particularly Christian and post-Christian groups.
The issue arose certainly in my time in the Church of England. I remember a priest who said you can be unitarian in the Church of England but not a non-realist (effectively a denial of the reality of God). Of course there were people including ordained who had come to a non-realist position.
So the issue is not what you become, and how you might wriggle with the intepretations, but when it comes to seeking training or a new post, or indeed going for confirmation.
I suppose you can just about be unitarian in the Church of England if you are strong on God and on Jesus as a human exemplar, but why not then have Jesus as a human exemplar of what God would be like? After all, God may not be the all-loving being but simply acts as God will (the sort of unlimited Islamic model) for which your protection is either belief or exemplary behaviour.
I've always settled on the view that you should somehow be able to affirm resurrection, incarnation and God in the material. You don't need to affirm bodily resurrection, because the texts are ambiguous, but you ought to be able to say that the texts are on to something happening. I came to the view that the texts demonstrated something that was not happening, other than in the views of the early Churches based on the original Jewish expectation and the Pauline twist.
Old Catholicism as created in small groups in Britain is probably similar but with plenty of add-ons (e.g. home-grown Pagan) and stretched edges, a sort of liturgy with relaxation about interpretation. Liberal Catholicism, with its early history of diving into Theosophy and Krishnamurti, and its consideration of magic along with the supernatural, can be a combination of the liturgical orthodox and all manner of reinterpretations and additions. Some of the 'higher' manifestations of Liberal Catholicism seem to go back into the wider reaches of the first hundreds of years of Christianity and even incorporating the spiritual and Gnostic.
In the Unitarians as such there aren't any boundaries, supposedly, but actually there are in some chapels (by practice, expectation, whom they hire), and in any case you are going to have to be comfortable by the use of theistic language, however it is intepreted. It has to mean something at least, otherwise it will get very tedious. It is relatively easy for it not to be supernatural, and to have a human-level focus, but the language is bounded about a lot. It is quite clear that prophetic religious figures are all human and subject to the same limitations and mistakes as the rest of us (this being so obvious it hardly needs saying), though some older interpretations minimise the limitations and emphasise the prophetic achievement.
There are many groups where it is very easy to join in and very demanding to become a member. The charismatic types are like this: culturally familiar but signing on the dotted line demands quite a hurdle to jump and keep jumping (beliefs and expectations). I remember how apparently progressive and welcoming the Baha'i's were but then you discover that the main figures are regarded, in the texts too, as infallible and then you discover the limits of the inclusivity (try and be gay in the full sense, for example, or be a woman and have a place in the Universal House of Justice) and you discover things like the Baha'is affirming something like evolution but not the full science of evolution and indeed the method of science - because of what the prophetic figures at the time didn't understand and yet they are given the privileged treatment of infallibility.
It is amazing how, though, people become inculturated to the group and adopt its views. Things that they did not believe as individuals they take on once committed to the group. Nevertheless, people do go through groups; they do even come out of the most demanding of cults. In strongly believing groups, people entertain private doubts very privately, and then discuss with a few trusted people (often to find they are not to be trusted) and then at some point there is marginalisation and isolation, until the group magnet has faded and they leave.
The necessity to leave (moving house, changing jobs) is often a means by which people drop former beliefs that they were once so willing to express. Churches know this, which is why they are keen to get people hitched up to the right kind of church in the new location. Churches may seek out the people who have moved from another area into theirs, as information is passed along.
I think that for some Unitarians there is a fading away. They attend less often, and then even less often. They are missed by the congregation, but given space people fade away and eventually they've simply broken the connection. This also happens in the more anonymous Christian places of worship.
I sometimes think that we are observing a period of fundamental transition from the inside, that really there is a death of the churches taking place. We can stress their positive benefits for personal support and reflection, and community building, but other than for these large and entertaining media type churches the sub-culture of church life is being lost.
It is actually quite difficult to enter a 'mainstream' church and understand what is going on and why. The eucharistic ritual and its language will be strange to many - it is an acquired taste (wherever performed). I still think Unitarians are trapped into a model that is part of a past late Victorian sub-culture, yet I am less able to say how to break free. After all, meditation groups and the newer Eastern groups are themselves small in numbers. I'm quite convinced that many of the collective beliefs are reproduced by individuals in expression, but in all practical terms they don't operate (in ordinary life, as ordinary explanations for things).
The process of secularisation (which is a complex analysis) is one which shifts those Church boundaries. To keep people in, you have to be more liberal and perhaps members become more culturally attached; to attract people in you have to be part of the easily understood contemporary culture and that means distinctiveness comes in other ways, particularly in jumping through the hoops of belief.
Perhaps the thinking ought to go in different ways entirely: for example, the most likely to come to attend a more standard church are the early retired. What sort of fellowship or ministry does that group require that would be reflective for their lives and time ahead? It is not then about beliefs at all, even if these are so often operating as boundary markers.
So the institutional boundaries of belief are shifting, but in the end churches may have to stop and settle at what they have got, and are forced into being more sectarian in that sense. All groups are destined to be small, and even the big ones are only big in terms of the percentage of the actively religious.
A view from the gallery - http://changingattitude.org.uk/wp-content/uploads/2017/02/GS-A-View-From-the-Gallery-75x42.jpg 75w" sizes="(max-width: 299px) 100vw, 299px" /> When I was a ...