REASONING: DRAWING IMPLICATIONS FROM OUR BELIEFS
The processes involved in judgment are crucial for us because they allow us to draw new information from our prior experiences. No less important are the processes of reasoning, in which we start with certain beliefs and try to draw out the implications of these beliefs: “If I believe X, what other claims follow from this?” The processes in place here resemble the processes that philosophers call deduction—when someone seeks to derive new asser-tions from assertions already in place.
Why is reasoning (or deduction) so important? One reason is that this process allows you to use your knowledge in new ways. For example, you might know that engineers need to be comfortable with math, and you might know that Debby is an engineer. With a trivial bit of reasoning, you now know something about Debby— namely, that she’s comfortable with math. Likewise, you might know that if it’s raining, then today’s picnic will be canceled. If you also know that it’s now raining, some quick reasoning tells you that the picnic is off.
These are, of course, simple examples; even so, without the capacity for reasoning, these examples would be incomprehensible for you—making it clear just how impor-tant reasoning is. In addition, reasoning serves another function: It provides a means of testing your beliefs. Let’s say, as an illustration, that you suspect that Alex likes you, but you’re not sure. To check on your suspicion, you might try the following deduction: If he does like you, then he’ll enthusiastically say yes when you ask him out. This pro-vides an obvious way to confirm (or disconfirm) your suspicion.
In several ways, then, the skill of reasoning is quite important. We need to ask, there-fore, how well humans do in reasoning. Do we reach sensible, justified conclusions? The answers parallel our comments about judgment: Examples of high-quality reason-ing are easy to find, and so are examples of reasoning errors. We’ll therefore need to explain both of these observations.