Naturalism & the Problem of Moral Knowledge

Here, I explain the problem with ethical naturalism: It can’t account for moral knowledge.*

1. Background: Ethical Naturalism

• Ethical naturalists claim that the nature of ethical properties (good, bad, right, and wrong) can be explained using entirely descriptive (non-ethical) concepts. E.g., maybe goodness is just the property of increasing the total amount of pleasure in the universe. (Notice how “increasing the amount of pleasure in the universe” doesn’t contain any evaluative terms.) Or maybe the rightness of an action just consists in its promoting the life of the agent. Or maybe goodness = that which we desire to desire. Etc. There are many possible naturalist views of this kind.

• Naturalists used to say that they could explain the meanings of ethical terms using non-ethical language. But they generally don’t say that anymore, because G.E. Moore refuted that view a long time ago. Example: Consider the question, “Is promoting pleasure good?” Notice that this question is meaningful, and notice that it does not mean the same as “Does promoting pleasure promote pleasure?” That shows that “is good” does not mean the same as “promotes pleasure.”

• Now naturalists usually claim that their theories are analogous to scientific theories, such as the theory that water = H2O. Notice that “H2O” does not explain the meaning of the word “water”. (Many people have understood the word “water” without knowing any chemistry.) However, it does explain the underlying nature of water (it’s a compound whose molecules contain 2 hydrogen atoms bonded to one oxygen atom).

For a popular defense of ethical naturalism, see Sam Harris’ The Moral Landscape. (I haven’t read it, but it defends ethical naturalism, and I assume that it’s more readable than typical academic presentations.) The view is also defended by academics such as (philosophers) Railton, Boyd, Sturgeon, and (legal theorist) Michael S. Moore.

2. More Background: The Knowledge Problem

Many people find moral knowledge puzzling. How do we know what is good and bad, right and wrong? Some of us say that you need to use “ethical intuitions” (see my book: https://www.amazon.com/dp/0230573746/).

Important point: Naturalists are specifically trying to avoid ethical intuition. They want to show how moral knowledge can be empirical. That is a central motivation for being a naturalist in the first place.

So here’s an initial thought: if, e.g., goodness is just the property of promoting pleasure, then, since we can empirically determine what causes pleasure, we can empirically determine what is good. I think Sam Harris’ view is close to that (using “wellbeing” in place of “pleasure”).

Problem: the above account doesn’t work unless you can explain how we know that goodness = causing pleasure. And you’d have to justify that empirically. In other words, say you have an inference like this:

P1. Democracy promotes pleasure (for the world overall) more than dictatorship does.

C.   Therefore, democracy is (prima facie) better than dictatorship.

(Don’t worry about whether “promoting pleasure” is the best naturalist account of goodness, or whether it should instead be something about “wellbeing”, “life”, etc. This is just for illustrative purposes; you can put whatever you want in for “pleasure”.)

Problem: C doesn’t follow from P1, unless you assume:

P2. Promoting pleasure is good.

I’m not denying P2; of course I agree that promoting pleasure is good. The question is how we know this. I would say we know this by ethical intuition. The naturalist is going to need some other account of how we know it. We’ve already rejected the idea that it’s analytic (sec. 1 above). So the naturalist is going to have to somehow claim that it’s empirical. What’s the empirical evidence for P2?

Naturalists can claim that P2 is true because promoting pleasure is “the nature of” goodness, but they still have to explain how we know that that is the nature of goodness. I.e., if P2 is based upon

P3. Goodness is identical with the property of promoting pleasure.

then the naturalist needs to tell us the empirical evidence for P3.

3. Inference to the Best Explanation

As mentioned above, contemporary naturalists like to draw analogies with scientific theories, such as the theories that water = H2O, heat = kinetic energy of vibrating molecules, and lightning = a discharge of electrons from clouds to the ground. These are all “theoretical reductions” that are justified empirically, essentially because these theories help to explain some observations.

Maybe moral theories can be justified analogously, by inference to the best explanation. So now we have a debate about whether moral claims can ever explain anything we observe. (See the Harman/Sturgeon debate from a few decades ago.)

Initial naturalist thought: Moral facts explain lots of stuff. For instance, Adolf Hitler ordered the Holocaust because he was evil, and not, for example, because he couldn’t control his actions, or he had some major misunderstanding, etc. For another example, the U.S. abolished slavery because it was unjust and not, for example, because it was economically inefficient, or because the slaves revolted and were too powerful to defeat, etc. (See https://philpapers.org/archive/HUEALR-2.pdf.)

Initial non-naturalist thought: No, moral evaluations never explain observations. For instance, if you say slavery was abolished because slavery was unjust, that’s just loose talk. The more precise statement is that slavery was abolished because people thought that it was unjust. I.e., it is only psychological facts about us that are really explanatory. If we think slavery is unjust, but it’s really just, then exactly the same things will happen as will happen if we think slavery is unjust and we’re right. The actual justice or injustice makes no empirical difference. In the Hitler example, the true explanation is the psychological fact that Hitler had intense, racial hatred. The idea that such a motivation constitutes evil adds no extra explanatory power. If Hitler had such hatred but this didn’t constitute evil, then exactly the same stuff would happen as if it was evil.

Naturalist response: Two points. First, it’s long been accepted in philosophy of science that a scientific theory doesn’t predict any observations by itself; rather, you usually have to use a whole complex of auxiliary assumptions, including other, background theoretical beliefs, to derive observational predictions from a theory. Thus, it should be okay to do this with moral theories too. Now, given our background beliefs, the theory that Hitler is evil predicts that he would be more likely to do stuff like ordering the Holocaust. It’s not an objection to this to point out that this relies on background beliefs about evilness.

Second, one of the keys to “good explanation” is unification. Ex.: if you want to explain why a certain peg won’t fit into a certain hole, the best explanation might be “you can’t put a square peg into a round hole” (with a diameter smaller than the diagonal of the square). The best explanation isn’t to cite the specific configuration of all the elementary particles in the peg, etc. The reason the “square peg/round hole” explanation is better than the microphysical one is that the “square peg/round hole” explanation lets you know what to expect the next time you try to put another square peg (with a different configuration of particles) into another round hole. It unifies cases that intuitively belong together, which the microphysical explanation doesn’t.

Moral explanations might be like this too. Each case of evilness has some underlying, psychological characteristics that constitute the evil (but different psychological configurations in different cases). So why not just cite the underlying psychological configurations? Because the explanation that cites someone’s moral character unifies cases that intuitively belong together.

So that’s how morality might have explanatory value.

4. What’s Wrong with That

Ethical naturalism is a very counterintuitive view; almost no non-philosopher would come up with it. Most people sense that morality really isn’t like science. But it might not be so obvious exactly why. So now I’m going to explain that.

First, let me tell you about how we know “water=H2O”. People figured that out in the 1800’s (for millennia before that, they thought water was an element). There were two crucial experiments.

a.          Combustion: First, you take some “inflammable air” (that’s what hydrogen used to be called) and some “de-phlogisticated air” (that’s what oxygen used to be called) and put them in a container together. Introduce a spark into the container, and a fire occurs. After the fire, there is less gas, and there is condensation on the walls of the container. The condensation turns out to be water, with the same mass as the gas that got used up.

b.         Electrolysis: You apply an electric potential difference to a sample of water. Bubbles of gas start forming at both the cathode and the anode. The water gradually gets used up, and the total mass of gas produced equals the mass of water consumed. The gas coming from the cathode turns out to be inflammable air; the gas appearing at the anode is de-phlogisticated air.

That’s the main evidence that water is composed of these two other elements, which we now call hydrogen and oxygen. Now, is there anything like that with naturalistic accounts of morality? Are there experiments that they can explain, analogous to the electrolysis or combustion experiments?

No, there aren’t. A key point is that, in the case of water, alternative theories could be formulated, but these theories could not explain the same evidence. For instance, if you think that water = NaCl, then you can’t explain in any natural, not-completely-bizarre way why electrolysis of water produces hydrogen and oxygen gas.

In the moral case, you can think of alternative theories, and they explain exactly the same observations in perfectly analogous ways. Let’s say someone proposes to explain why Hitler ordered the Holocaust by appealing to Hitler’s evil, along with the theory that extreme racial hatred constitutes (a form of) evil. Someone with an alternative value system could posit that extreme racial hatred constitutes good, and this person could then explain exactly the same events, equally naturally. To the extent that the “evil” theory unifies observations (per sec. 3 above), the same unification could be achieved by the “good” theory.

The naturalist’s explanations are like the following. Suppose that, instead of the combustion experiment, Lavoisier had supported his theory about the composition of water with the following observations: “My table is currently wet. Given that H2O constitutes water, the fact that H2O is on the table explains the observation of the wet table. Similarly, H2O explains why there are rivers and lakes, why my thirst was quenched this morning, etc. So that’s why we should believe in H2O.”

That’s like the naturalist’s moral explanations. You can substitute an alternative theoretical reduction and “explain” exactly the same facts.

*Based on “Naturalism and the Problem of Moral Knowledge,” Southern Journal of Philosophy 38 (2000): 575-97.