As a review, the original intent of the group under discussion was to facilitate growth among the members and thereby the body. As the members were selected to be mature Christians with appropriate experience, the subject matter is in depth, intense and studied over an extended time (a year+). As progress is made the group develops a cohesive pattern of discussion and exploration. This enhances the process. Thus the goal of the group, growth within each member, results in the form of the group, which is by definition restricted to particular people and presentation format. As the work progresses, the situation becomes more and more ‘exclusive’ in the sense that the members develop the accumulating knowledge and skills which are required to continue. Further it becomes clear that the effects of the work are being felt in other areas of each member’s life, increasing the effectiveness of this work. This is a cause for rejoicing.
Now the ‘Christian’ fun begins…
Into the situation comes an unannounced stranger with almost no background in the subject matter, drawn by word of the exciting work that the group is doing which has spread in one of the associated congregations. Further, this person does meet the original criteria for participation (eg. availability, consistency, background, general familiarity to the members since things are already underway). Yet they are intrigued by the work, think that it would be profitable for them, and feel that they will just join in.
In some ways they are not to be faulted since most church’s regard group exclusivity as a social sin, irrespective of the reasons. Inclusivity is regarded as a prime fruit, if you will, which of course is more Post Modern than Christian (but that is another discussion).
What would be the result if they did simply join?
Since the structure supporting the original intent was designed to facilitate cohesive growth resulting from an ongoing accumulation of knowledge and experience, and since this process requires cumulative work, the insertion of a new member would likely have a number of affects, all counterproductive. It would: bring the necessity to re-cover previous material on a consistent basis; require teaching basic material that is assumed at the start in all members; disrupt some or all comfort in discussion that has been built in the group to date; generally interrupt the flow of group thought. The group would simply not be the same group and would be forced to re-coalesce. Further, if the person did not attend regularly the disruption would repeat.
The overall result would be to reduce the actual and potential level at which the group can operate and the any growth.
Next, if this new philosophy of necessary inclusion were forced to continue, and more people joined spontaneously, the group goals would become unreachable and the group would be effectively changed over time to basic training. The longer the existence of the group, the farther this change would progress.
So, to the question. Is there a Christian principle that requires groups to be inclusive and that thereby makes special interest groups somehow sinful? I would say no. Further, I would say that this all too common miss-interpretation of hospitality and welcoming is error.