TESTING MORAL PREMISES
But how can we evaluate moral premises? After all, we cannot check them by consulting a scientific study or opinion poll as we might when examin- ing nonmoral premises. Usually the best approach is to use counterexamples.
If we want to test a universal generalization such as “All dogs have tails,” we can look for
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counterexamples—instances that prove the gener- alization false. All we have to do to show that the statement “All dogs have tails” is false is to find one tailless dog. And a thorough search for tailless dogs is a way to check the generalization. Likewise, if we want to test a moral premise (a variety of universal generalization), we can look for counterexamples.
Examine this valid moral argument:
1. Causing a person’s death is wrong.
2. Individuals in a deep, irreversible coma are incapacitated persons.
3. “Pulling the plug” on someone in a deep, irreversible coma is causing a person to die.
4. Therefore, “pulling the plug” on someone in a deep, irreversible coma is wrong.
Premise 1 is the moral premise, a general moral principle about killing. Premises 2 and 3 are non- moral premises. (Premise 2 is entailed by Premise 3, but we separate the two to emphasize the impor- tance to this argument of the concept of person- hood.) Statement 4, of course, is the conclusion, the verdict that causing someone in a deep coma to die is immoral.