A while ago I wrote a post advocating that modern Christians should self-identify by wearing a cross or something similar.
But today I realized that this is, or soon will be, unneccesary.
Because the degree of self-identification among non- or anti-Christians is becoming so clear and obvious that Christians will soon be identifiable merely by exclusion.
Devout adherents of other religions have often self-identified in the West - ultra-Othodox Jews, Moslems, Sikhs, Hundus and so on.
So that is easy.
But it is characteristic of the late stage of secular cultural Leftism that anti-Christians are increasingly marking and labelling themselves as such: typically by their inversion of the transcendental Goods of Truth, Beauty and Virtue.
(The transcendental Goods of Truth, Beauty and Virtue are not - of course - distinctively Christian; but they are intrinsically Christian. Therefore any deliberate, proud, public flouting of any of them is with a high probability self-labelling as anti-Christian - in the absence of self-labelling of being a member of another religion. )
Anti-truth is proudly displayed in the use of plastic surgery and bodybuilding drugs - to project lies about a person's age and aptitudes.
To the extent that a person advertizes their enthrallment to fashion they display their inauthenticity, their subordination to prevailing dishonesty above timeless truth; their willingness to mould themselves in accordance with worldly norms.
Anyone who deliberately deploys technology (make-up, hair dye, clothing) and ingenuity (to assemble these) such as to display an image that is (say) fifteen years younger than their true age, is very probably not Christian.
Anti-beauty is projected by the proud advertisment of self-mutilations of various types - tattoos, piercings, deliberate uglification with make-up or dye, drunkenness, intoxicating drug usage...
(Of course, a person may mutilate himself and repent to become a real Christian. And they may have been multilated by others - perhaps when young. It is never too late to repent. But Natural Law (as a component part of Christianity) is incompatible with the un-repentance involved in the proud and deliberate display of self-mutilations.)
(And of course being ugly is normal for humans, since beauty is rare and evanescent. It is deliberate uglification, purposive desecration of beuaty, which is sinful, hence anti-Christian.)
Anti-virtue is typically (although not excusively) displayed in terns of public, proud, displays of allegiance to any of the tenets of the sexual revolution - whether specific, or a general and indiscriminate sexualization of appearance or behaviour.
Furthermore, anti-Virtue nowadays includes public displays of Leftist markers; since we now realize that Leftism is inrinsically anti-Christian.
(This was not always the case, and in the past there were real Christians who were socialists, for instance - but for the past several decades (at least) Leftism has evolved to exclude Christianity.)
So all manner of Leftist causes may be marked and proudly displayed - whether banners, posters, books, badges, dress styles, or whatever - and these can be used as indicators that the user has a very low probability of being Christian.
In conclusion, the small minority of Christians will - before much longer - be able to recognize each other by a double negative: simply as being the only ones who are not clearly self-labelled as not-Christians.