2
about political life, I think, we can hardly afford to avoid testing our reactions to
artificial cases. Indeed, limiting ourselves to reflection about real-world cases would
be too theoretically costly. Since our basic ideas about political are disorganized and
even inconsistent, we cannot easily do without a method well-suited to finding some
counterpoise between our intuitions and more abstract principles.
I. Species of Thought Experiments
Political philosophers have several motivations for constructing imagined,
hypothetical cases. The principal one is suggested by the activity of scientific
experimentation itself. We hold constant certain factors to isolate the particular
features that are morally decisive – to identify the moving parts of a moral argument.
If we confined ourselves to real-life cases, inquiry into the basis for our moral
judgments would be severely – I think unacceptably – constrained. For one thing,
there exists considerable consensus on a surprisingly wide range real-life cases.
2
Where deep disagreement or uncertainty persists, we need to identify with precision
the site of contention. Thought experiments allow us to hold all conceivable factors
constant except for the one being examined. We thus aim to eliminate the “noise”
that is part of the richness of empirically gathered cases, avoiding the plurality of
variables that may be tugging our intuitions in various directions. This enables us to
test whether the factor in question has bone fide moral relevance. But in so doing,
we necessarily construct cases that have a certain thinness.
If the method succeeds, and we pick out the factor that affects the moral status
of a case, we have made room for an argument by analogy, or a morally significant
disanalogy. Our initial case-specific judgments can be then be subsumed under more
general principles. Gradually, we can achieve greater coherence among our
convictions about political morality. The assumption that drives this desire for
2
Jeff McMahan, “Moral Intuition,” The Blackwell Guide to Ethical Theory
(2000), pp. 100-101.
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