One big problem I notice frequently with people is that people want to take grammatical rules of word structure and universalize them. When we see an ending on a word, we know what that ending means from other words, and we attempt to apply the meaning to the word in question. This isn’t a bad idea, but it can backfire.
“It seems to me that a minimum requirement for Christianity is a belief in the divinity of Christ.”
Why: is the minimum requirement for being a Kantian a belief in the divinity of Kant?
I say: let people define themselves as Christians as they please as long as they explain what they mean by that.
The major qualm I have with this is linguistic: Calling oneself a Christian is relevantly different from calling oneself a Kantian. There is perhaps a sense in which they are similar, a sense of agreement in values and ideas (i.e. a Christian agrees with the values Christ set up, and a Kantian agrees with the ethical system that Kant proposed). But there is a level above this in which Christian entails quite a bit more than just agreement in this fashion. Christianity is not just an association with ideas; it is also generally an affiliation with a set of core beliefs. Although there are some widely contended beliefs within theological circles, the divinity of Christ is not generally disputed by those who are affiliated with Christianity (the religion that is based upon the teachings and work of Christ and his apostles).
The context of the comment is in talking about whether or not certain Founding Fathers (Jefferson is here the specific one in question) could rightly be called Christians, deists, or some other term (‘theistic rationalist’ is one suggested). The comment being responded to here asserts that Jefferson denied the divinity of Christ and that therefore he cannot be truly thought to be Christian in the normal context. I agree. The commenter above seems to be arguing by analogy that the “-ian” affix does not indicate such a belief, but that certainly misses the point: even if the affix doesn’t entail the belief, the association indicated by the term does in this case. And even if one rejected that point, it still wouldn’t be true that Jefferson could be called a Christian by this sentiment because Jefferson (to my knowledge) never called himself a Christian under any definition and in many cases disassociated himself from Christians.
I will say one thing in some agreement: There are plenty of affixes using to make an associative noun like this, e.g. -ian, -ist, and there really isn’t any rhyme or reason to their use except for personal preference. There is perhaps a tendency toward -ian for associations with people, e.g. Aristotelian, and -ist for general ideas, e.g. transcendentalist, but this is neither hard nor fast. I find that people want to have those sorts of rules – indeed, I desire them myself as well from time to time – but there simply isn’t any prescriptive way of using them. So one might use “Christian” to describe one’s agreement with Jesus’ social and ethical mandates toward others while denying his divinity, miracles, etc., but using that definition in the public sphere is largely problematic because Christian means something different. Those wishing to make such a connection would do well to heed this warning.