The Big Picture
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Syllogisms are not the only kind of logical argument— they’re just a par-
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ticularly simple form that will suffice to make our point.
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The first two statements in a syllogism are the premises of the argument,
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while the third statement is the conclusion. An argument is said to be valid
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if the conclusion follows logically from the premises. In contrast, an argu-
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ment is said to be sound if the conclusion follows from the premises and the
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premises themselves are true— a much higher standard to achieve.
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Consider: “Pineapples are reptiles. All reptiles eat cheese. Therefore,
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pineapples eat cheese.” Any logician will explain to you that this is a com-
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pletely valid argument. But it’s not very sound. An argument can be valid,
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and even interesting, without telling us much that is true about the real
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world.
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If we were to try to put a derivation of ought from is into the form of a
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syllogism, it might look something like this:
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1. I would like to eat the last slice of pizza.
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2. If I don’t move quickly, someone else will eat the last slice of
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pizza.
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3. Therefore, I ought to move quickly.
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At a casual glance this seems like a good argument, but it’s not a logically
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valid syllogism. The two premises are both “is” statements— my desire to
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eat the last slice, and the likelihood that I will miss that chance if I don’t
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move quickly, are both factual claims about the world, whether or not they
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are actually true. And the conclusion is undeniably an “ought” statement.
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But if you look past the everyday meaning of the sentences to their underly-
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ing logical content, something is missing. Premises 1 and 2 don’t actually
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imply the conclusion 3; what they imply is “Therefore, if I don’t move
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quickly, I will not get what I like.”
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To make the conclusion follow validly, we would need to add another
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premise, along the lines of:
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2a. I ought to act in such a way as to bring about what I
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would like.
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With this addition, the argument becomes valid. It’s also no longer a can-
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didate for deriving ought from is— an “ought” statement appears right
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there in the new premise. All we’ve done is to derive an ought from an
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ought plus a few is’s, which isn’t nearly as impressive.
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That’s the problem with attempting to derive ought from is: it’s logically
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impossible. If someone tells you they have derived ought from is, it’s like
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someone telling you that they’ve added together two even numbers and
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obtained an odd number. You don’t have to check their math to know that
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they’ve made a mistake.
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And yet, it happens all the time. Over and over again, before and after the
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appearance of Hume’s famous passage, many people have triumphantly
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declared they have finally cracked the code and shown how to derive ought
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from is. Smart, knowledgeable people, with interesting things to say. But
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somehow they have all gone wrong.
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Physicist Richard Feynman liked to tell the story of meeting a painter
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and asking him about his craft. The painter boasted that he could mix red
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and white paint together and get yellow. Feynman knew enough about how
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color works to be skeptical, so the painter fetched some paint and com-
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menced with mixing. After a bit of effort and nothing but pink paint to
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show for it, the painter mumbled that he should probably add a touch of
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yellow to the mix, to “sharpen it up a bit.” At that point Feynman under-
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stood the trick— to get yellow out, you put a bit of yellow in.
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The painter’s gambit is the same basic move that has been used to per-
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form the logically impossible, deriving ought from is, many times over the
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centuries. One presents a set of incontrovertible “is” statements, then sneaks
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in an implied “ought” statement that seems so extremely reasonable that
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nobody could possibly deny it. Sadly, all statements about what ought to
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happen can (and will) be denied by somebody, and even if not, that doesn’t
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prevent them from being ought statements.
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A classic example was offered up by John Searle, of Chinese Room fame.
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Here is Searle’s version of the kind of deductive argument we examined
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above:
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1. Jones uttered the words “I hereby promise to pay you, Smith,
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five dollars.”
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2. Jones promised to pay Smith five dollars.
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3. Jones placed himself under (undertook) an obligation to pay
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Smith five dollars.
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4. Jones is under an obligation to pay Smith five dollars.
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5. Jones ought to pay Smith five dollars.
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You see the magical appearance of “ought” in the last line, even
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though all of the other lines were about “is.” Where did the sleight-of-hand
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occur?
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It’s not that hard to find. Just as we had to imagine a new premise 2a
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above, Searle is relying on a hidden premise between 4 and 5:
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4a. All else being equal, one ought to do what one is under an
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obligation to do.
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Searle actually admits the need for a premise like this, right in the text of
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his paper. But he thinks it doesn’t count as a premise, since it’s a “tautology”—
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> something that is automatically true by the definitions of the terms involved.
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Searle is claiming that what it means to say, “Jones made a promise to do
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something,” is simply “Jones ought to do something” (all else being equal).
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That’s not true. Hopefully the equivocation is clear. Up in premises 1– 3,
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the idea of “placing himself under an obligation” referred to a certain fact
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about the world, a sentence that Jones uttered. But now in 4– 5, Searle wants
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us to treat an “obligation” as a moral command, a statement about what
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ought to happen. He’s using the same word in two different senses, to trick
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us into thinking that factual statements about what happens can somehow
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lead to evaluative conclusions about right and wrong.
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This example is worth belaboring because it stands in for an impressive
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number of attempts to derive ought from is over the years. Inevitably, the
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argument introduces just a tiny bit of prescription into their list of descrip-
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tions: the painter sharpens things up with a touch of yellow.
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This inherent flaw in deriving ought from is has been pointed out many
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times. The list of thinkers who claim to have successfully pulled off the
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trick is long and distinguished; they aren’t simply making elementary
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mistakes. Lurking in the back of their minds is usually some kind of justi-
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fication along the lines of “Okay, there is some hidden premise that intro-
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duces an ought into my list of is’s, but surely we agree that this particular
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hidden premise isn’t so bad, right?”
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It wouldn’t be so bad if it weren’t for the fact that, when brought out
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into the clear light of day, the hidden evaluative premises don’t seem to be
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universally true. Quite the contrary; they tend to be conspicuously conten-
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tious. The reason why deriving ought from is should be thought of as a
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philosophical felony, rather than a simple misdemeanor, is because these
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hidden premises deserve our closest scrutiny. They are, more often than not,
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where most of the action is.
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You might be tempted to think that Searle’s hidden premise 4a seems
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pretty unobjectionable, but let’s examine it more closely. Surely there are
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some kinds of obligations that one ought not to carry out— when they were
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made under duress, or when they would grossly violate some other moral
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precept. Searle would say that such examples don’t count, because of the “all
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else being equal” clause. So what exactly does that clause mean? He tells us:
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The force of the expression “other things being equal” in the
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present instance is roughly this. Unless we have some reason for
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supposing the obligation is void (step 4) or the agent ought not
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to keep the promise (step 5), then the obligation holds and he
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ought to keep the promise.
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So you ought to do what you are under an obligation to do— unless
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there is some reason you ought not to do it. This doesn’t seem like a useful
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foundation for moral reasoning.
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We shouldn’t hide or downplay the assumptions we make in order to get
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moral reasoning off the ground. Our attempts to be better people are best
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served if those assumptions are brought out into the open, interrogated,
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and evaluated as carefully as we can manage.
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A modern twist on the ought- from-is campaign is to claim that morality
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can be reduced to, or absorbed by, the practice of science. The idea is some-
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thing like this:
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1. Condition X would make the world a better place.
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2. Science can tell us how to achieve condition X.
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3. Therefore, we ought to do what science tells us to do.
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In this case, the hidden assumption would appear to be:
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2a. We ought to make the world a better place.
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This might seem like a tautology, depending on your definition of the
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word “better.” But whether we put the hidden assumption into a statement
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such as this one, or bury it in the definition of “better,” we are still making
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some positive claim that something ought to be done. Such claims cannot
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be grounded on factual statements alone. Who decides what is “better”?
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Proponents of this technique will sometimes argue that all we’re doing
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is making some reasonable assumptions, and science makes reasonable as-
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sumptions all the time, so what we’re doing really isn’t any different. That’s
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missing an important aspect of what science is. Consider the following
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statements:
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• The universe is expanding.
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• Humans and chimpanzees share a common ancestor.
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• We should work to allow people to lead happier and
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longer lives.
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All of these statements are, by some lights, true. But only the first two
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are “scientific.” The reason is that each of them could have been false. They
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are not true by definition or assumption. We can imagine possible worlds
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in which the universe was contracting, or in which there were species like
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humans and chimpanzees that had not evolved from a common ancestor.
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We decide whether such statements are true or not by empiricism, abduc-
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tion, and Bayesian reasoning— we go out and observe the world, and update
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our credences appropriately.
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We don’t imagine carrying out experiments to decide whether we should
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work to allow people to lead happier and longer lives. W
e assume that it’s
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so, or we try to derive it from a related set of assumptions. That crucial extra
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ingredient separates how science works from how we think about right and
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wrong. Science does require assumptions; there are certain epistemological
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precepts, like our trust in our basic sensory inputs, that play an important
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role in constructing stable planets of belief for working scientists. But the
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assumptions that suffice to get science off the ground don’t do the same
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trick for morality.
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None of this is to say that we can’t address “ought” issues using the tools of
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reason and rationality. There is an entire form of logical thought called in-
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strumental rationality, devoted to answering questions of the form “Given
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that we want to attain a certain goal, how do we go about doing it?” The
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trick is deciding what we want our goal to be.
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One attractive suggestion was put forward by Bill Preston and Ted Lo-
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gan, as played by Alex Winter and Keanu Reeves in the movie Bill & Ted’s
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Excellent Adventure. They proposed the timeless moral axiom, “Be excellent
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to each other.”
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As foundational precepts for moral theorizing go, you could do worse.
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It’s tempting to brush aside concerns about the foundation of morality on
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the grounds that we know moral goodness when we see it, and what’s really
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important is how we go about achieving it.
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But there are important reasons why we have to do a little bit better than
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Bill- and- Ted-level philosophizing. The truth is that we don’t ultimately all
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agree on what constitutes happiness, or pleasure, or justice, or other forms
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of being excellent to each other. Morality and meaning are areas where
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foundational disagreement doesn’t arise just by someone making a mistake;
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it’s real and inevitable, and we need to figure out how to deal with it.
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It’s tempting to say, “Everyone agrees that killing puppies is wrong.” Ex-
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cept that there are people who do kill puppies. So maybe we mean “Every
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reasonable person agrees . . .” Then we need to define “reasonable,” and real-
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ize we haven’t really made much progress at all.
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The lack of an ultimate objective scientific grounding for morality can
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