Test of Explanatory Necessity: Useful or not?

According to test of explanatory necessity, the appropriate way to test whether there are moral facts is to see whether we need to suppose the existence of moral facts anywhere in our best causal explanations. Some philosophers think this is a good test of whether there are moral facts, and think that moral facts pass the test. Others agree that this is a good test, but think that moral facts fail it. Still other philosophers think that moral facts fail this test, but that it is a misguided test.

In this paper, I discuss Nicholas Sturgeon’s view as an example for the first position, Gilbert Harman’s for the second, and John McDowell’s and Thomas Nagel’s views as examples of the third view.

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Philosophers disagree on whether the test of explanatory necessity is an appropriate test of whether there are normative facts. It’s the test of whether we need to suppose the existence of normative facts anywhere in our best causal explanations of anything. Harman, Sturgeon, McDowell, and Nagel disagree on whether to accept this test and if moral facts pass it. I’ll first explain each of these philosophers’ points of view and then evaluate.

Harman subscribes to Ethical Naturalism but doesn’t argue for it in his paper. He compares scientific and moral cases to show a major difference between scientific and moral claims. The scientific case can be tested through observation, whereas the moral case can’t. In the moral case, we can explain observation with reference to observer’s psychology and sensibility alone. Observation doesn’t provide evidence, and moral principles alone don’t explain my observation. Thus, if the test of explanatory necessity is a good test, it then follows that moral facts fail the test, so there are no moral facts.

Sturgeon is a non-reductive ethical naturalist. He thinks one might accept ethical facts are natural facts without asking for a reductive definition in terms of, for example, physics. We don’t require reductivism for other disciplines like psychology. Sturgeon thinks the test is good and that moral facts pass it. He thinks moral facts play a role in explaining our moral beliefs. For example, Hitler’s actions can be explained by him being morally depraved. In other words, if Hitler wasn’t depraved, he would have different psychology, thus most likely would act differently. Sturgeon says it’s implausible for Harman to claim Hitler being morally depraved has no explanatory power about his actions.

McDowell and Nagel both believe it’s a misguided test and that moral facts fail it. McDowell is a proponent of Sensibility theories. He claims moral judgments can be understood by analogy with judgments about secondary qualities, which are properties that can be understood only in terms of a disposition giving rise to a certain subjective state. For example, redness and tartness are secondary qualities. He thinks the test is a poor test because values can’t be credited with causal efficacy, so they play no role in causal explanations. Causal explanation is not the only way of explaining as there are various understandings of behavior. We don’t have to causally explain everything about me and in the world, but we have to make things intelligible in order to understand. He proposes an intelligibility test for reality by asking whether the properties in question must be invoked in explanations which in a larger sense attempt to make our responses to the world intelligible to ourselves. Nagel is a non-naturalist realist who thinks there are truths independent of our thinking. However, reasons and values never play a role in the best explanation of anything and shouldn’t be understood as entities or properties. The test is too narrow a conception of the kinds of facts there are.

I agree with McDowell and Nagel, and I don’t think the test of explanatory necessary is a good test. There are various types of facts in the world, and I don’t think we know all of them. The test is too narrow because we know very little about the nature of reality, so how can we make a causality test to see whether there are any normative facts. I also don’t believe normative facts play a role in our best causal explanations because that undermines the role of our psychology and motivation. The intelligibility test McDowell suggests seems like a more appropriate test than the test of explanatory necessity.


“The Nature of Morality” by Gilbert Harman

“Moral Explanations” by Nicholas Sturgeon

“Values and Secondary Qualities” by John McDowell

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