Thinking and Deciding

RULES AND TRADEOFFS 357
People who think they want to follow lexical rules, no matter what, may, after
reflecting, find that in fact they simply have a very high subjective weight for one
dimension as opposed to another. They do not really think that one dimension has
absolute priority. Consider the claim that life should come before everything else.
Suppose that a health insurance company (in determining what treatments its policies
will cover) has a choice of saving the life of Mr. Smith by paying for a heroic operation
that will cost millions of dollars or else paying for treatment to cure arthritis
in 1 million policyholders. (I pick arthritis because it is painful but not usually life
threatening.) If we wanted to put life ahead of everything else, we might still balk
and decide to pay for Mr. Smith’s operation. Now let us suppose, however, that the
success of the operation is not a certainty but rather a probability (p). Suppose that
p were .001. Would we still prefer the operation? What if p were .000001? It seems
that there must be a value of p sufficiently small so that our preference would switch.
If such a value of p exists (above zero), then we are, in fact, willing to trade off the
two attributes at issue — life and pain. That is, we are willing to say that some finite
interval on the pain scale is equivalent to a nonzero interval on the life scale. The
nonzero interval on the life attribute is just the interval between no change at all and
a p probability of saving a life. This interval is equivalent to (or less than) the interval
between the status quo and the arthritis cure, on the pain scale.
Some of our resistance to the idea of making tradeoffs is caused by our attachment
to certain prescriptive rules of decision making. Lexical rules may prevent us
from sliding down slippery slopes, in which one decision, justified in its own right,
sets a precedent for similar decisions that are not well justified. A decision analysis
might tell an official, for example, that the gain from taking a small bribe is greater
than the harm that this single act would cause. The slippery-slope rule would tell
the official, however, that accepting one bribe might be like trying cocaine “once”; it
might become a habit, and then the harm would be much greater. Similarly, people
argue that if we allow life to be sacrificed for one reason (mercy killing, for example),
we might be more willing to allow it to be taken for other reasons (lack of
enforcement of safety regulations, for example).
Instead of invoking the slippery-slope rule, I would argue that the decision analysis
that led to taking the bribe was seriously incomplete, because it ignored a major
consequence of the choice in question, namely, its effect on later decisions about
bribes. Therefore, we do not need the “slippery-slope” argument, if we do a thorough
analysis. Also, when we decide to favor one dimension (or goal), such as life,
we are always ignoring some other dimension, such as pain, and that bias could lead
us down a slippery slope as well. If we insist on taking small chances to save lives
when we could be curing pain instead, we might become callous to pain. Slippery
slopes can work both ways. To neglect this fact is to fail to be sensitive to evidence
on both sides of the question.
Nonetheless, lexical rules can be useful prescriptive devices for self-control. As
a rule of thumb, it may be helpful to us to think that certain things always “come
before” others — but it is difficult to justify such rules as normative in decision
making (Baron, 1986).