Some apologists have made the claim that an apologetic argument(s) that only demonstrates the existence of God with probability, albeit a high probability, are deficient in a major way: the unbeliever still has an excuse.
This inexcusability, of course, is taken from Romans 1.
It is alleged that if the apologist only shows the probability of God's existence, albeit a high probability, the unbeliever can go before God on judgment day and claim he had an excuse for not believing.
It seems that those who argue thus grant Bertrand Russell's argument before the throne:
God: Why didn't you believe, Bertie.
Bertie: Not enough evidence God, not enough evidence.
There was some evidence, just not enough. God's existence was only probable.
Of course Bertie didn't think God's existence probable, let alone highly probable, but I trust my general point about apologists granting his claim stands.
By why think this?
First off, the text isn't even discussing apologetics in general and arguments for God's existence in particular.
Secondly, isn't the fact that God's general revelation to man is clear, exceedingly clear, what grounds the inexcusability? Even if every apologetic argument in the world failed to show that God's existence had a probability of .1, wouldn’t man still be without excuse?
Third, is it even true that probability can't ground inexcusability or moral culpability? Ignorance of the law is not an excuse?
Furthermore, suppose that a man had an argument presented to him by an auto mechanic to the effect that his brakes would probably fail the next time he stepped on them. The man asks how sure the mechanic is. The mechanic says that he's pretty sure. "How sure?", says the man. The mechanic says, "You have a 90% chance the brakes will fail the next time you press the pedal." Now, say this man ignored the mechanic, took his children, and got in his car to go home. Unfortunately, the mechanic was right, the car failed to stop at the intersection, and the car was t-boned, landing the man's children in county hospital in critical condition. Now say you go to visit this man, who's a friend of yours, while he's waiting for news on his children at the hospital. Say the mechanic was also a friend of yours and he called you and told you what he told the man who crashed. Wouldn't you rightly, and with indignation, storm up to the man and say something like, "What were you thinking Mike! Didn't Moe at the auto shop warn you about your brakes? What's your excuse!?" You obviously mean the last line rhetorically as there is no excuse. But the man, Mike, looks at you and says, "But I had an excuse, the argument Moe gave only yielded a 90% probability that the brakes would fail. One can't be held inexcusable for failing to form a belief that is only probable, albeit highly probable."
Mike's reasoning seems self-evidently false to me. Especially considered morally rather than epistemologically (and Paul is making primarily an ethical point).
That's at least my rough thoughts on the matter.