But for everyone who lacks either the time or the inclination to sift through all that stuff, here's my summary of the basic points being argued. Bear in mind that I'm representing Randal's points as I understand them, and I should allow for the possibility that I haven't understood him as he intended. If there are any doubts, you'll have to just read his comments for yourself.
Randal's premise is that an objective moral law exists. This law is as much a part of reality as anything else we experience, crucial to our understanding of human nature, and evidence that God exists (because as the old argument goes, you can't have a moral law without a moral lawgiver).
To support his premise, he appeals to our rational intuitions about what is good or evil. While he seems to accept (as any rational person must) that we don't always intuit this law precisely, he nonetheless asserts that our intuition of moral 'law' reflects an ontological reality. In his words:
[Our] moral perception of basic moral facts is among the most secure things we know and is no less "nebulous" than our rational intuition of mathematical facts.
My objection is rooted in something called (deep breath) the isolation objection to coherentism. Coherentism is a branch of philosophy which states that a belief is epistemically justified if it is internally consistent. The isolation objection basically states that a belief can be internally consistent, yet still not actually reflect reality. From the Stanford Encyclopedia of Philosophy:
There is an obvious objection that any coherence theory of justification or knowledge must immediately face. It is called the isolation objection: how can the mere fact that a system is coherent, if the latter is understood as a purely system-internal matter, provide any guidance whatsoever to truth and reality? Since the theory does not assign any essential role to experience, there is little reason to think that a coherent system of belief will accurately reflect the external world. A variation on this theme is presented by the equally notorious alternative systems objection. For each coherent system of beliefs there exist, conceivably, other systems that are equally coherent yet incompatible with the first system. If coherence is sufficient for justification, then all these incompatible systems will be justified. But this observation, of course, thoroughly undermines any claim suggesting that coherence is indicative of truth.
Still with me?
Here's the problem with Randal's argument: science has often shown that reality is counter-intuitive. What philosopher could have ever arrived at the bizarre nature of subatomic particle behavior – quantum entanglement, wave/particle duality, quantum uncertainty, etc. – by any process of "rational intuition"? Our brains essentially give us a model of reality. This model can be said to be dependent on our subjective frame of reference. That is to say that the reason you can't get to quantum uncertainty by way of rational intuition is because we don't exist on a quantum scale. The models our brains construct are reliable enough, but imperfect – prone to biases that cloud our judgment and incapable of intuiting reality in frames of reference beyond our own.
The problem Randal faces is that since reality can be (and often is) counter-intuitive, and since our "rational intuitions" can only give us a tiny slice of the pie of reality, you simply cannot use logical inference to prove that an objective moral law exists. Even if the logic of the argument is air-tight (internally coherent), it may not actually reflect reality. It's entirely plausible that instead of reflecting some "moral law", our moral intuitions reflect traits selected for by evolution intermingled with our complex interdependent social hierarchies. How could we know which proposition is true (if either)? Obviously our intuitions alone cannot tell us, so we need a methodology that allows us to test the their validity by examining data and making falsifiable predictions – something like, oh I don't know... science.
Toward the end, I got the impression that Randal thought I was arguing that I could categorically conclude that there is no moral law. I don't think I can do that. However, I think that if there were a moral law, then it would be objectively accessible to us – that is, it could be understood using the tools of science. It's possible that a moral law exists, but if it's not objectively accessible to us then it might as well not exist. I don't believe in a moral law because I think:
- There's no evidence that it exists in the first place
- Morality is better understood scientifically
- If it does exist, no one seems to know how to objectively access it