Ethical Naturalism

Ethical naturalism is the metaethical theory that all moral properties (morally right, morally wrong, morally good/bad, etc) are identical to natural properties (physical properties). In other words, every moral property could be discovered by a scientific analysis of physical properties. It is obvious that moral properties could be realized in different ways in different possible worlds. For instance, what moral goodness looks like in some possible world W could be different than here, at least in the physical make-up. Imagine that the agents on
W are made of completely different stuff, perhaps they are silicone based beings instead. If they have moral properties, then those moral properties would be realized by different physical properties than they are here in the actual world. The ethical naturalist gets around this by positing a disjunctive natural property as that which is identical to a moral property. So, moral goodness for instance is [either N1 or, N2 or, N3 or, . . . . or, Nm] where the N's are natural properties. Moral properties are still identical with natural properties, the natural properties are just quite complex. However, the ethical naturalist must also say that there is no possible worlds where moral properties are realized by non-physical/non-natural properties. This means that there would be no possible world where God exists (where God has at least one morally good property), Descartes' evil demon genious exists (since it has some morally bad properties), or a world where substance dualism or idealism is true and there are moral properties had by such beings. Now these theses are not very philosophically popular, but it is quite another matter to claim to have utterly refuted them and show that there is no possible world where they are true, yet this seems to be the burden of the ethical naturalist.
This post is cross-posted at Moral Realism http://moralrealism.blogspot.com/ if you want to follow discussion there.