(Sorry for the hiatus. I’m back to finish our conversation.)
Your reasoning in the opening paragraph seems circular: “We assume this because evidence.. tells us.. that there is no evidence that any ‘extra-natural’ force acting upon us or inspiring us to be good.” You’re using the preconceptions of non-theistic evolution as evidence that there is no evidence for an extra-natural point of origin for morality (and the universe)? You didn’t answer my question of why this is the break in the pattern that all laws require a law giver. Do you consider this merely an illusion, that morality is not actually “law” in the same way as traffic laws or human rights laws? Is there anything objectively wrong with torturing babies for fun? My evidence that a law giver must exist comes from the shared human experience that all laws come from a law giver, and then using logic and evidence (well trafficked in writings of those who study philosophy of religion) that a transcendent law such as “torturing babies is always wrong” that is true even in the face of human extinction, regardless of whether there are any humans around to abide by that law, must have a transcendent law giver. Now, if you want to argue that torturing babies for fun is merely taboo and collectively frowned upon, and not transcendently wrong, be my guest.
Re: Churchland, I never argued that our moral laws come from reading the Bible or any other sacred text and then obeying it. I argued that they are written on our hearts — or encoded on our conscience, if you like. The sharedness of the golden rule between worldviews and religious systems is evidence of this. Cane knew it was wrong to kill his brother Abel, without having any of the Laws of Moses or the commandments of Christ to guide him.
Re: your real-life version of my island thought experiment, you don’t actually give an answer to the challenge about why we call hand-chopping barbarous, or even explain how you know that the answer isn’t rooted in anything extra natural. Is it because you believe in non-theistic evolution? Again, this is circular. If God exists, then evolution (if Darwinian macro-evolution did indeed take place) can’t and won’t be able to debunk his existence. So you can’t use evolution as a means to disqualify God from being the arbiter or good and evil. Why do you and I agree that chopping off a hand is not the right solution for theft? And actually, we do more than that; we not only say “that’s wrong for me,” but we say “that’s wrong for them — they should not enact such barbaric penalties. We should stop them or encourage them to stop, or at the very least privately believe they should stop.” Why?
I asked myself “Is there truly a Celestial Being who has endowed me with certain moral principles and drives, and if so what is the evidence for this claim?” And then I considered your claim that nobody in the history of the world has ever given a satisfactory answer. My conclusion: Are you kidding? Countless authors and thinkers of all stripes have agreed/reasoned/admitted that if there is transcendent moral law, it reasonably requires a transcendent moral law giver. So either these laws are not transcendent (as I argued above, they are only taboo and unliked), or they are transcendent from something outside of the natural. It’s that cut and dry. What’s your take?