The Big Picture

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The Big Picture Page 67

by Carroll, Sean M.


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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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  W h At I S A n d W h A t Ou g h t t O b E

  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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  •

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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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  T H E B IG PIC T U R E

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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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  W h At I S A n d W h A t Ou g h t t O b E

  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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  •

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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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  T H E B IG PIC T U R E

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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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  •

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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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  W h At I S A n d W h A t Ou g h t t O b E

  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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  •

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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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  T H E B IG PIC T U R E

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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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