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These three rules for generalizing, taken together, illustrate a point already men-tioned: the open-ended character of induction. Unlike a deductive argument, an induc-tive one is not self-contained. Its strength is affected by the context of other knowledge we possess. The truth of the premises does not guarantee the truth of the conclusion, and the degree of support the premises provide for the conclusion depends on factors not contained in the argument itself. It is always possible to strengthen an inductive argument further by finding additional positive instances, especially if they increase the variety of the sample (rule 1). But the strength of the argument is dependent on our diligence in looking for disconfirming evidence (rule 2). Its strength also depends on the initial plausibility of thegeneralization, which is determined by the body of related knowledge we have (rule 3). This is not a defect of induction. But it does mean that inductive reasoning puts a special premium on integration, on looking beyond the argu-ment itself to see how it fits with the rest of our knowledge.The three rules we have just examined are applicable to generalizations of most kinds. Appropriately enough, they are general rules. But there are different kinds of gen-eralizations, and for each kind we can formulate more specific rules. In the next section of this chapter, we will study the rules for identifying causal relationships. In Chapter 14, we will look at statistical generalizations.SUMMARY Rules for Generalizing1. Make sure the sample from which you gen-eralize is sufficiently numerous and various.2. Look for disconfirming as well as confirming instances of the generalization.3. Consider whether the generalization is plausible in light of other knowledge you possess.EXERCISE 12.1A. Evaluate each of the following generalizations inductively, drawing on your own experience. If you think you don’t know enough to tell whether it is true or false, identify the kind of evidence you would need in order to decide. In each case, indi-cate how each of the rules would guide your reasoning.❋ 1. The food at restaurant X [pick one you know] is lousy.2. Italians are hot-tempered.3. The soil in my garden is highly acidic.❋ 4. Dogs always go around in circles when they lie down.
12.2 Causality4235. Ms. or Mr. X [pick someone you know] works well under pressure.6. None of the clothes in my closet is new.❋ 7. Doctors have high incomes.8. Heroes in tragic drama always have a fatal flaw.9. All religions involve belief in a god or gods.❋ 10. All geniuses are eccentric.11. Price controls produce shortages.12. Without antitrust laws, indus-tries would be dominated by monopolies.B. The Acme Corporation has employees with different jobs—assembly-line workers, bookkeepers, salespeople, managers, etc.—with different levels of education. Each of the cards below represents an employee. On one side is the person’s job; on the other side is the person’s level of education. Which cards would you need to turn over to test the generalization that all the salespeople are college graduates?