Suggestions and Goals:

One of the more surprising realizations for many students is that a belief can have evidence but not be known to be true. For many students, if you tell them that a belief has evidence, they think you are telling them that it must be true, that some group of experts have verified the belief beyond a shadow of doubt. This misunderstanding is another indication of the black and white framework with which many people face the world. A belief either has evidence and is true, or it has no evidence and is not true.

One of the major goals of this chapter is to do more than cover the technical specifics of recognizing and distinguishing inductive from deductive arguments and related skills. This chapter should encourage students to have tolerance for a wide diversity of opinion but constrain that tolerance by adopting a process of ongoing criticism. Furthermore, students should be encouraged to avoid beliefs that give us the illusion of rest, decisiveness, and final closure, and see that inductive reasoning is rational provided the goal is to constantly test and correct, to constantly be open to learning how to make our inductive inferential claims better, and to accept beliefs that based on their support are likely to be reliable guides to the future.

One of the best examples I know of is the cigarette smoking and lung cancer example. It is one of the best examples for illustrating the careful, critical nature of science, of how a massive amount of evidence can exist for a belief, even though we cannot be absolutely certain that the belief is true. With a little work, though, you should get the point. Based on the evidence, we have a reliable belief with which to contemplate a decision -- "Cigarette smoking is a principal cause of lung cancer" -- and although it is possible, it is unlikely that three or four decades from now we will find out that we were wrong and that cigarette smoking is good for human lungs. Thus, a person could still rationally decide to smoke. Perhaps they do not plan or want to live long, or they are unable to quit. However, reasonable people would no longer fool themselves that there is nothing wrong with smoking cigarettes or think that whether it is harmful or not is just a matter of opinion.

Concerning the technical specifics, I find that many students first need help understanding the nature of inductive evidence, a generalization, how one confirms or refutes a generalization, and that there are different tests of generalizations in terms of strength. The barrel full of apples example should help you: 

1. Understand the open-ended nature of inductive inference -- even after a lot of tests and confirmations for a belief, we could be wrong about the belief being true.
 
2. That some types of evidence are stronger than others -- a representative sample is stronger than induction by enumeration.
 
3. That even though we lack certainty with inductive inference our conclusions can be rational -- after pulling out 10 to 50 rotten apples in a representative fashion, we would have a very good reason to believe that all the apples are rotten. Here we should also remember the hat problem in Chapter 1. There we saw that x would be inductively reasonable to choose a red hat, if he saw two white hats.
 
4. That there is no crisp cut-off point for knowing exactly when an inductive argument is weak or strong, that inductive reasoning usually involves a gradual accumulation of evidence and is always tentative and ongoing. Some may argue that 10 rotten apples are enough, some 50, and many might agree that it is somewhere in between. But all would agree that 50 is better than 10.

Other Reminders:

1. A key point in this Chapter is that there is no such thing as a valid inductive argument. All inductive arguments are technically invalid. However, it is very important to remember that one can be rational using inductive arguments provided they are strong inductive arguments. Almost all of the important beliefs that we have about the world are the result of inductive arguments. Scientists believe that the Darwin's theory of evolution (natural selection), current theories about the age and size of the universe, and the connection between smoking and lung cancer are all very reliable beliefs based upon very strong inductive evidence.
 
2. We use the terms strong and good vs. weak and bad, rather than valid or invalid to refer to inductive arguments. Look at #’s 6 and 7, Ex. III, pp. 108-109 in the textbook. Obviously #6 is a very weak inductive argument and #7 is much stronger.  In terms of the concept of a reliable belief discussed in Chapter 2, we should be able to say that the reasoning in #7 provides us with a foundation for practical action.  A detective would have something to go on.  He or she would probably start interviewing and investigating the people who knew the victim.  But it would be very premature to act on the reasoning in #6.
 
3. In recognizing inductive arguments look for these types of situations. All of the following would be inductive situations.
   

Premises                     Conclusion

One, Some, Most                All

Past                                     Present

Past and Present                  Future

Time sequence                     Causal Connection

Any argument that fits one of these situations will be inductive, because the conclusion is a generalization that goes beyond the type of evidence offered in the premises.


4. Darwin's theory of natural selection is very controversial in the United States.  It is important that you understand why scientists believe that biological evolution is a very reliable belief based on very strong inductive evidence.  We don't have time to go into every detail, but at a minimum, see some examples of evidence via some dramatic pictures of Argentinosaurus,  Jobaria,  Archaeopteryx, and how scientists read the earth.  For a complete discussion (optional) of Darwin's theory see Chapter 3, Science and the Human Prospect.
   

For more on the worldview of modern science (optional), see Chapter 1, Science and the Human Prospect.  See some movies on where we live in our universe and galaxy.

For more on scientific method (optional), see Chapter 2, Science and the Human Prospect.

For more on the dangers of smoking cigarettes, see the stories of super model Christy Turlington, Debbie Austin video, smoking in China, what is in a cigarette, radiation in a cigarette, and comparative pictures of a smoker's lung with a non-smoker's lung.