I'd like to know what will all sotapanna have in common with each other. And the same for arahants (both for separate, please, not comparing a sotapanna with an arahant).
What are the common grounds in terms of what has been uprooted? What do they share in terms of understanding, ideas and views (independently if they are not attached to those views)?
I ask this, because I've noticed that there are lots of differences between all the ideas about what should a sotapanna/arahant know, be, feel and think, for example. And, according to the level of confidence/attachment/understanding of those asked about what a sotapanna is, they will be more on the defensive, disparaging any other idea conflicting with theirs, stating that a sotapanna/arahant is only what they think it is, with more or less grounding on suttas.
For an outsider, it may almost seem like a discussion based on "No true scotsman" fallacies.
EDIT: Thanks for the answer given so far! I wanted to add another point.
Now that OyaMist has written about interpretations on those common grounds, I realize that that might be exactly the main source of problems. Since we're using texts written in a language not used as vernicular in current societies; since most concepts can be interpreted in multiple ways; and since there are a lot of discussion (with more or less logical arguments or irrefutable evidence) about the "authenticy" of some texts or discourses, most conclusions seem to fall into what feels the most coherent to the particular follower, or into what seems to produce the best results.
For example, some say one cannot reach stream-entry without attaining 1st jhana. But I think this criterion becomes problematic, to say the least, when the problem of interpretation and definition occurs in the exact same way when talking about what jhana is or is not.
If that's the case, how to differenciate between the most relevant/fundamental and secundary/optional interpretation for those common grounds?
EDIT 2: Just for the sake of context, and to give some (possibly) hints to a potential answer, maybe we can rephrase the question about the minimum common grounds for all sotapanna as: What is the minimum knowledge that Right View HAS to contain in order to really be Right View?
I'd appreciate any help on this issue. Thanks in advance!