David Hume’s Muddle Part III

Is The “Is-Ought” Gap a Real Problem for Ethics

This is my third and final rebuttal of Hume’s “is-ought” law. This technical argument was saved for last. If I presented it first some folks would blow it off as a technical sleight-of-hand. Besides it was necessary to examine the meaty arguments of Hilary Putnam, John Searle and Julius Kovesi first. With their help we see the concept of fact and factual descriptions as theory-laden and linguistically complex in contrast to Hume’s narrow empirical view. This final argument should be easier to follow from within that context.

This has been a long argument to rebut Hume’s guillotine which is one of the most influential parts of Hume’s philosophical work. It’s certainly the most influential part of his discussion of morality. My goal, of course, was to present a convincing refutation of his “is-ought” law which I describe as a confused muddle in its very set up. In short, it’s simply a useless sideshow.

You may have noticed in my past posts that I referred to Hume’s so-called guillotine in different ways: as an argument, an assertion, a thesis, a principle. Frankly it’s hard to put a label on it. Calling it an argument is really not accurate. Nevertheless, it is based on Hume’s basic claim that a “fact” is something perceived by the senses—something that is known only by sense perception. We explored that extensively in Part I. Consequently Hume’s guillotine is a conclusion which he draws from that claim. And it’s validity, of course, is dependent on the validity of that underlying claim about the nature of facts.

We could call it Hume’s “law.” That works. So for now, let’s call it a law, specifically a rule of good practice—like the rule that a chef ought keep his knives sharp. So, like a chef keeping his knives sharp, an ethicists should mind the “is-ought” gap. That sounds about right.

So if it makes sense to call Hume’s “is-ought” law a rule of good practice then what kind of rule is it? Well, it’s not a natural law like the laws of gravity or the speed of light. Those laws can be objectively verified by science. And it’s obviously not a rule imposed by a legislature like a speed limit or the law against littering. The most appropriate choice is to label it a “normative” rule. That’s because it works as a “standard” of judgment. That is, it’s a standard that guides us in the proper practice of an activity. In our case it supposedly guides us in the correct way to practice philosophy—specifically ethics.

That should remind us that back in Part I we explored Hilary Putnam’s claim that science itself depends on values—which he called “epistemic values.” Putnam argued that certain epistemic norms function as standards in the correct practice of science. We “see through the lenses” of those normative standards, says Putnam. Such norms help us to decide among scientific theories as to what we ought to believe as true about the physical world. These epistemic standards include “consistency,” “coherence,” “plausibility,” “reasonableness,” and “simplicity,” among others. As Putnam points out, these concepts are not physical facts nor are they mathematical concepts—they are normative or value considerations.¹

However, if we have correctly described Hume’s “is-ought” law as a normative standard, then that creates a problem for Hume. Morality is normative. And, as we know, Hume’s basic claim is that we cannot “perceive” ethical norms like (his example) a willful murder. Hume claims “there is no matter of fact in the case.” The so-called wrongness of a murder is simply not an object of perception.² That’s Hume’s foundational position. Unfortunately that makes Hume’s “is-ought” law a self-refuting proposition. By Hume’s own thinking, if there is no “fact of the matter” supporting the norm of murder, then likewise there is no “fact of the matter” supporting his “is-ought” norm either. It is also not an object of perception. Sorry David, it looks like you shot yourself in the foot with that one! But it doesn’t matter. Your norm is based on a totally mistaken understanding of the nature of facts and factual descriptions anyway. So it’s useless to begin with!

Well, that’s it. That was my three-part rebuttal to Hume’s claim of an “is-ought” gap. At the end of the day, it’s just a useless sideshow diversion—a meaningless but stubborn holdover from our empiricist-positivist heritage. It’s time we moved on to a genuine study of ethics.

1. Putnam, Hilary, The Collapse of the Fact/Value Dichotomy, Harvard, 2002, p. 28-33.

2. Hume, David, Treatise of Human Nature, https://davidhume.org, Book 3 Part 1, sect 1.