I approached it from a purely “logical/reasonable” position with my Southern-Baptist father-in-law, shortly before he died. It really made him think and he died before ever answering me.
I gave him the example of a man who is on his way home from work. He gets a call from his office friends reminding him that today was the last day of work for Tom, a co-worker, and that they are all having a few drinks to say goodbye. He says he will be right over. Just then, his wife calls and asks when he will be home. Rather than say he is going to have a few drinks (work has kept him away from home, and the wife was hoping he would be home a little earlier than usual), he tells a “white lie” about having left something at the office and having to go back and get it. The man truly did not want to lie, but he did not want to start a fight and disappoint his wife either. And there was no element of having an affair, going to a strip club - just going tell a co-worker goodbye. The moment he hangs up with his wife, he is struck by an 18-wheeler and is killed instantly.
I asked my father in law: assuming this guy died with no MORTAL (and I begged his indulgence on this: for the sake of this hypothetical, agree some sins are far worse than others) sin on his soul, in what state would his soul exist: hell, purgatory, or heaven.
He agreed there could be no more than three (although he believed in only two), unless one was an atheist, and that was not part of the discussion. He agreed that in Revelation, St. John stated clearly that “nothing unclean” could enter heaven, and that reference was obviously about someone’s soul - not their body or clothes. And he finally agreed that the “lie” the man had told his wife was not really that serious, especially given the parameters of my hypothetical.
So - where did he go? My father-in-law said “heaven”. I asked how could that be. He said: “Because Jesus died for our sins and the man was forgiven”. I then pointed out: “How could the man be forgiven for having lied to his wife, considering he had been killed instantly before having a chance to even ask God to forgive him?”
Of course, my father-in-law grew silent, as he had not really thought of such a situation before. He again said that “Jesus died for our sins”, and I agreed, “no doubt”. But what happens to a person’s unclean soul that is not unclean with mortal sin, but nevertheless has unconfessed sin on it? He thought a bit, and said he would have to “get back with me on that”.
It was a good conversation to me because I believe I truly made him think.