In my opening statement for last night’s Caplan-Hanson Debate, I relied heavily on a couple of grostesque hypotheticals:

endorses an endless list of bizarre moral claims.  For example, he recently told me that “the
main problem” with the Holocaust was that there weren’t enough Nazis!  After all, if there had been six trillion
Nazis willing to pay $1 each to make the Holocaust happen, and a mere six
million Jews willing to pay $100,000 each to prevent it, the Holocaust would
have generated $5.4 trillion worth of consumers surplus.

Let’s consider another
example.  Suppose the only people in the
world are Hannibal the millionaire, a slave trader, and 10,000 penniless orphan
slaves.  The slave trader has no direct
use for his slaves, but likes money; Hannibal, on the other hand, is a ravenous
cannibal.  According to Robin, the “optimal
outcome” is for Hannibal to get all 10,000 orphans and eat them.

If you’ve ever taken a
class in moral philosophy, you’ve probably heard weird examples like these
before.  Normally, these examples lead
people to back away from their pet moral theories.  Robin’s devotion to efficiency is so strong,
however, that he will bite any bullet you present.  The most he’ll say in his own defense is that
he is “Merely serving as an advisor to help people get what they want,” but the
fact remains that faced with the preceding examples, he’d advise genocide and cannibalism.

I suspect that many attendees saw these examples as “cheap shots.”  But when I pressed Robin, he predictably bit both bullets.  His main objection was just that my examples aren’t very relevant to actual policy analysis.  What’s the point of bringing up genocide and cannibalism?

My response: Weird hypotheticals are philosophers’ equivalent of controlled experiments.  When a scientist wants to test a physical theory, he sets up weird laboratory conditions that make it easy to find an exception to the theory.  Similarly, when a philosopher wants to test a moral theory, he sets up weird examples that make it easy to find an exception to the theory.  Philosopher Michael Huemer explains it best:

How, one might
ask, can we draw
conclusions about how the world really is from purely hypothetical
premises, i.e., premises about some imagined but not actual

This objection is vaguely felt by many who object to
thought experiments in philosophy in general, but it is a logical
error. You can validly deduce a categorical proposition from
hypothetical premises.

For example:

A -> (B -> C).

B -> not-C.

Therefore, not-A.

is a valid form of inference, where the “->” stands for the “if …
then” relation (i.e. “If x were true, y would be true”) …And this form of inference
is relevant to the way hypotheticals are used in philosophy to test
moral principles. The typical form of thought-experiment-based
arguments in moral philosophy is as follows: “If moral theory T
were true, then
in situation S, it would be right to do A. But in situation S, it
would surely be wrong to do A. Therefore, T is false.” Notice
that this form of argument is perfectly valid: the conclusion
deductively follows from
its premises (it’s a variant on modus tollens). Notice also that
both premises are hypothetical – i.e., both are about what would be
right if so-and-so were the case. But the conclusion is
categorical. (emphasis mine)

When I point out that Robin’s theory implies that the rightness of the Holocaust depends on the number of Nazis, then, I’m not trying to smear him as a Nazi sympathizer.  I’m saying that his theory has crazy implications, so his theory is false and he should revise it.  End of story.

P.S. Here’s my complete debate archive.