If you're a regular reader you may have been following these thoughts of mine over the last few months, but it you're just jumping in a quick summary of the basic idea I'm arguing for.
In short, human values are metaphysical in nature in that they have to be taken as "goods" that are self-evident, non-negotiable givens. To be clear, metaphysical here doesn't mean supernatural or religious. Metaphysical here means axiomatic, things that simply have to be assumed as first principles to get the analytical system off the ground.
If this seems unclear, a good illustration about what I'm talking about is Euclidean geometry. For the logical system of geometry to work--Remember proving things in High School with "QED"?--some basic axioms have to be assumed. For example, an axiom of Euclidean geometry is that the shortest distance between any two points is a straight line.
Now, notice two important points about the relationship between axioms and reasoning in Euclidean geometry.
First, the entire logical system cannot get to work without axioms provided as inputs, as fuel for the logical machine. This illustrates something that I argue holds in exactly the same way for ethical and moral reasoning: Reason alone is not enough. Reason is just an analytical, logical, computational capacity. Reason can suss out fallacies and help you weigh options, but reason can't tell you what is right or wrong independently of how you value various goods when they come into conflict. In the same way that reason without axioms can't lead you to a geometrical truth, reason alone cannot tell you what is right or wrong independently of values. Reason is just a computational tool, but it's a tool that needs raw materials to work with.
This limitation of reason is illustrated by a second feature of Euclidean geometry. Specifically, if you change the axioms and you change the truths. You may or may not know this, but Non-Euclidean geometry was discovered when mathematicians rejected the fifth axiom of the Euclidean system. This was the parallel postulate, the axiom that two parallel lines could never intersect. Well, when you reject that postulate, when you allow a parallel line to cross at some distant point, what you have is a geometry for curved space. This Non-Euclidean geometry for curved space is what Einstein famously turned to to come up with his theory of General Relativity, gravity as causing curvatures in spacetime.
My point here is how different axioms created different geometries, different truths and proofs. Both Euclidean and Non-Euclidean geometry are equally logical and rational, but they describe different realities because they start with a different set of axioms.
I am arguing that a similar thing happens in moral and ethical reflection. Two competing ethical systems can be equally rational. Both systems can make appeals to "reason." For the most part, then, the differences in ethical systems isn't that one is rational and the other irrational. In this sense, a secular, non-religious ethical system and a religious, theistic ethical system can be equally rational. Both reason from axiomatic, first-principles toward ethical conclusions. Any differences in ethical conclusions between these or any other ethical systems would be due to different axioms, as with Euclidean and Non-Euclidean geometry. One ethical system defines "the good" one way and an alternative ethical system defines "the good" in an different way. Just like Euclidean geometry accepts the parallel postulate and Non-Euclidean rejects it.
All that to say, appeals to "rationality" and "reason" in ethical debates is really beside the point. The fundamental issue is how one defines "the good," the fundamental axioms that give you the raw material for ethical reflection and decision making, from the personal to the political.
The point I've been making across various posts is that everyone, theist and atheist, are involved in this metaphysical task, in declaring and specifying "the good," the evaluative, non-negotiable givens that will guide ethical reasoning. Before you can start "reasoning" you have to specify your values, and how those values are ranked should they come into conflict.There's no way to avoid this fundamental task. Oh sure, you can try to say that a process of reason produced your values. But that just backs up the problem. We can ask you to show your work, to display all the inputs and steps of that prior process of reasoning, what axioms provided the input and what computational steps were executed to get to the position you currently espouse.
At some point, unless you're a nihilist, you'll drill down to the basic inputs, to the metaphysical foundation, to the givens, to the moral axioms upon which your ethical systems stands.
