Some great posts, and I haven’t much to add.
He said that the problem was is that all believers assert that they are right.
It sounds like your friend doesn’t adequately understand what a religion is. When someone follows a particular religion, they
bind themselves to a particular creed and group (in our case, the Church). This binding is of one’s total self: one’s moral, social and personal life is subsumed under the faith. If this is the case with religions, isn’t it reasonable that a religious follower should believe that he or she is right, and have no cowardice in asserting that? Does he believe it is better for someone to give their lives totally to some other but doubt the truth of it? Would he (or she) enter a marriage with a someone and yet doubt his (or her) spouse’s fidelity and love?
Now, it seems that your friend is fully convinced of his own position and doesn’t mind asserting that he is right over all other religions and religious followers. Is there a bit of hypocrisy here?
My friend is a believer in total subjectivism. He thinks that the only truth is that there is no truth.
As everyone has noted, subjectivism (especially global subjectivism), like relativism, is self-refuting and so cannot be true.
He also thinks that it is arrogant to assert the beliefs of a religion because we cannot possibly know until the next life.
Whether it is arrogant or not to assert such claims is, frankly, irrelevant. Being arrogant means being proud, boastful and thinking you and your religion are superior to others and belittling theirs. To be honest, I don’t see many religions doing this. Most religions are pretty honest about their truth claims and hold other faiths in at least a modicum of respect. To me, it is frequently atheists or secularists who are arrogant in their claims, condemning and belittling all religious believers. Just compare, for instance, Richard Dawkins, Daniel Dennett and Christopher Hitchens to John Paul II, Fr Robert Baron and William Lane Craig.
But anyway, as I said, whether the believer is arrogant or not is not really the point. The question is: are their religious claims
true? He says that we cannot possibly know until the next life. This is where you need to work some apologetics with him to show him that this isn’t the case, that there are good arguments and evidence for the truth of Christianity and that we can with confidence know that the Church’s claims are true.
And then, you can retort: how does he (or she) know that his (or her) claims and subjectivism are true?