How do metaphysical naturalists approach ethics?

Question

I am wondering about traditions of ethics which might incorporate naturalism or skepticism.

As far as I understand, the Academic Skeptics, in particular Carneades and Cicero, held that there was no way to know anything for certain, but also held that you could draw conclusions about good and evil from available evidence. They did not think that the existence of a moral good was completely subjective, and they also did not think that the existence of moral goods required a supernatural agent. From the position of the Academic Skeptics, you could derive an ought from an is.

This point of view seems to be consistent with metaphysical naturalism. As the Stanford Encyclopedia of Philosophy puts it,

From the Hellenistic point of view, theology is part of physics. An account of god is part of an account of the natural world (as such, it is unrecognizable as ‘theology’ from the point of view of later theologies). Human beings and their cognitive faculties are natural parts of a natural world. They are organic and functional parts, interconnected with the other parts of the large whole which the universe is. A mind-world-gap (of the kind envisaged in the Cartesian tradition) is inconceivable. Each ‘mind,’ and that is, rational soul, is an integrated physical part of the physical world.

My question is two-fold. First, is my understanding of the ethical position of Cicero correct, and second, are there modern schools of philosophical thought that follow this tradition? To clarify the second question further, are there modern metaphysical naturalists who maintain that questions of good and evil are meaningful?

Answer 1

I don't know of any philosophers who fit the criteria, largely because "metaphysical naturalism" implies a physical reductionism when it comes to mind, which leaves no room for free will. Thus, there are no ethical issues to be considered: "ought" reduces to "is".

EDIT: Since the question has been reframed a bit, I'll attempt to flesh out my question in a slightly different direction.

It seems, from reading between the lines, that the question is actually about the grounding of an ethics that does not rely on a supernatural agent (such as a deity.) This is actually quite different than specifying metaphysical naturalism, which is a much more constrained view.

For example, Kantian ethics do not require reference to a deity, nor do Aristotelian ethics or Buddhist ethics; however, none of them insist that mind can be reduced to physical phenomena. The latter is an extreme position held by very few philosophers, and raises all kinds of problems, not the least of which is a nexus for free will-- if the mind is purely physico-mechanical, we are forced into a determinist position, and ethics becomes irrelevant.

This latter argument is made quite eloquently by Raymond Tallis in his recent book, "Aping Mankind", which shows very effectively the limits of physical reductionism when it comes to minds.

So: if you are looking for an ethics which is compatible with atheism, there are many to choose from. But if you are insisting on a metaphysics which is purely physical, there's no real need for ethics, as there are no persons to speak of: only so many atoms bouncing off each other in varying conglomerations.

SECOND EDIT: To clarify: Cicero and Carneades are not, in my reading, physical reductionists. Although they reject supernatural agents, they do not reject human agency, and this agency is tied up in a conception of mind that allows mind to influence matter-- which violates physical reductionism.

Physical reductionism is an extreme variant of non-supernatural metaphysics. There are a number of notable non-supernaturally-grounded ethical systems out there, but these all require an ethical agent who is capable of choice. This cannot be reconciled with physical reductionism, as there is no locus of choice-- how can a mechanical process make a free choice? Even those philosophers who claim to hold a reductionist position (like Penrose) get all hand-wavy when it comes down to these matters (i.e. quantum stuff). If one believes that the mental supervenes on the physical, then conscious decisions cannot be causative, but must simply be side-effects of physical objects following the laws of physics; one must either be a dualist, or an eliminativist (and argue that mental events do not exist at all.) Jaegwon Kim makes this case quite cogently.

Answer 2

Ayn Rand and Leonard Peikoff hold both these views that you can get to an is from an ought and that morality is objective.

http://aynrandlexicon.com/lexicon/morality.html

http://aynrandlexicon.com/lexicon/logic.html

http://aynrandlexicon.com/lexicon/is-ought_dichotomy.html

As for metaphysical naturalism, I'm not sure what you mean, but whatever you mean this will answer your questions about these philosophers...

"The branch of philosophy that studies existence is metaphysics. Metaphysics identifies the nature of the universe as a whole. It tells men what kind of world they live in, and whether there is a supernatural dimension beyond it. It tells men whether they live in a world of solid entities, natural laws, absolute facts, or in a world of illusory fragments, unpredictable miracles, and ceaseless flux. It tells men whether the things they perceive by their senses and mind form a comprehensible reality, with which they can deal, or some kind of unreal appearance, which leaves them staring and helpless."