Some say that since this side of the grave we can’t know who is correct, Christians can’t claim to know the truth. At first glance this sounds like a statement that comes from humility. Instead this is pure arrogance. It’s similar to the analogy of the blind men and the elephant. Seems like a story with a profound point until you realise that the one telling the story thinks that he and he alone has the answer - he’s the only one who knows that it’s an elephant while everyone else is blind.
So too with those with those who say that we can’t know truth. If the person was saying, “I don’t know which religion is true,” that would come from humility. To say, “No one can know,” is to infer that you know everything there is to know about religion, or any other belief system for that matter. That kind of dogmatic statement is usually reserved for atheists who throw in the added piece of arrogance in saying, “Because I’m a Bright and you’re not, I can tell you that you are wrong and I am right.”