[fwdude]

Of course you can tell who is a believer or not. It is stupid to say you can’t. We are told to judge, to make distinctions. It’s a recipe for disaster when we claim we can’t. That is license for all manner of evil to be tolerated in a body.

[Mrs. Don-o]

We have qa duty to judge, and I know that judging justly is an obligation. However we can only judge justly what we can objectively know: ideas/ideologies as good or evil, acts (conduct) as right or wrong, speech as true or false.

There are two things we cannot know because we are not God: people's interior dispositions (unless they tell us); and people's eternal destiny (i.e. we can't say if a person is damned.)

So even if a person's observable behavior can be judged, the inner state of their soul cannot. You don't know if the person acted on the basis of ignorance or delusion, if they were under inner or outer coercions, if they were drunk or on drugs or just plain crazy. And you can't know with moral certainty whether they've just been repented and been forgiven the 70x7th time.

Judge exterior things justly. Don't presume to judge things only God can know. Such as, whether they are believers. Sometimes it's obscure to the human eye.

[Elsie]

Of course you can tell who is a believer or not.

Possibly; but the QUESTION was about CHRISTIAN...