Carly Simon may not have had in mind the exclusivity of truth claims when she wrote those lyrics back in the 70’s, but that charge of vanity is also sometimes leveled at anyone who claims to be “right” about something, especially in the realm of morality. I read an opinion online recently that any one religion feeling their beliefs are superior to another is “egocentric and self-centered”. But it’s only egocentric and self-centered if all views are equal. If, for instance, Jews were actually correct that Jesus was not God incarnate, but only a blasphemous rabbi, or if the Muslims were actually correct that Jesus was a prophet and nothing more, then I would not say they were egocentric for saying they were right and I was wrong. On the contrary, their statement would then be rooted not in themselves, but in the objective truth that Jesus wasn’t really God (assuming for the sake of argument that was correct). This is actually the opposite of egocentrism and self-centeredness because the nature of objective truth means that we can be genuinely right or wrong based on the object we make a statement about, not our subjective opinion of the object. This is really other-centered rather than self-centered.
In fact, it’s the relativist worldview that is egocentric, as it seeks to define truth relative to one’s own standard. But some things really are independent of any standard we invent. Think of it this way: suppose I were color-blind and about to eat poison fruit that looked identical to a certain edible fruit except for the critical detail that they are the 2 colors I can’t differentiate. Should you, coming up to me right before I take the fatal bite (not being color-blind and knowing the danger I was in), refrain from telling me the truth for fear of appearing self-centered? No! First off, that would be selfless of you to try to warn me of the danger I was in. But I also wouldn’t call you self-centered because your warning was not simply your own personal opinion, but rather your awareness of the objective toxicity of the fruit. It’s poisonous whether or not either of us are aware of it, and whether or not either of us do anything with that knowledge. Regardless of whether I think the poison fruit will kill me, I’d still be dead in the morning.
Likewise, there’s another poison called sin that is killing each and every person on this planet, and there’s only one cure: Jesus Christ. It’s not self-centeredness, but rather selfless love, that motivates (or at least should motivate) Christians to try to warn people of the danger they’re in. “But”, you might ask, “don’t other religions think they are helping people just as much with their proselytizing, too?” Yes, I would say they probably do, and they are probably very sincere in those efforts. But that is precisely where objective truth comes into play. Being sincerely wrong doesn’t alter the consequences of our choices. And so it’s not vain or self-centered for the Christian to believe they’re right and others are wrong if their beliefs are grounded in the unchanging standard of God’s truth instead of their own opinions.
Some would accept that truth is conformance to reality, but then say that only applies to description, not prescription. In other words, moral values prescribing what is right and wrong are allegedly outside the scope of objective truth because these aren’t statements about “real” physical objects that can therefore conform to reality. Yet the same unchanging God who made all of our physical reality also prescribed certain behaviors as right and others as wrong, whether we agree with them or not. And if reality is that which exists, then if these laws have been decreed by God, and so exist, then morality is simply part of the non-physical portion of reality. Just as descriptions of the natural world will be truthful when they conform to physical (or natural) reality, behavioral prescriptions will also be true when they conform to that non-physical (or supernatural) reality.
In the general revelation of nature and the special revelation of the Bible, we have a unified message from the Author of all of reality. And our understanding of both nature and morality need to be rooted in God’s truth if we don’t want to be tossed about by every new wave of ideology that comes across the bow as we sail the seas of this life. Rather than self-centered vanity, this is a most humble reliance and focus on our Creator as the only transcendent source of Truth.