Chapter+IX

**Explanations and Inference**

 * Understand what inference to the best explanation is and how it differs from other kinds of induction.
 * Know what an explanation (including theoretical explanation) is and how it differs from an argument.
 * Appreciate how inference to the best explanation is used in all disciplines and in everyday life.
 * Be able to demonstrate how to use inference to the best explanation in many different situations.

**Theories and Consistency**

 * Know how to check an explanation for internal and external consistency.

**Theories and Criteria**

 * Understand the importance of using criteria to judge the adequacy of theories.
 * Be able to list and explain the five criteria of adequacy.
 * Be able to apply the criteria of adequacy to simple causal theories.
 * Know what an //ad hoc// hypothesis is.

**Telling Good Theories from Bad**

 * Memorize and explain the four steps in the TEST formula.
 * Recognize the importance of considering alternative explanations.
 * Be able to use the TEST formula to evaluate theories.

Chapter summary
Even though an explanation is not an argument, an explanation can be part of an argument -- a powerful inductive argument known as inference to the best explanation. In inference to the best explanation, we reason from premises about a state of affairs to an explanation for that state of affairs. Such explanations are called theoretical explanations, or theories. To be worthy of consideration, a theory must meet the minimum requirement for consistency. We use criteria the criteria of adequacy to judge the plausibility of a theory in relation to competing theories. The best theory is the one that meets the criteria of adequacy better than any of its competitors. The criteria of adequacy are testability (whether there is some way to determine if a theory is true), fruitfulness (the number of novel predictions made), scope (the amount of diverse phenomena explained), simplicity (the number of assumptions made), and conservatism (how well a theory fits with existing knowledge). Judging the worth of a theory is a four-step process called the TEST formula: (1) Stating the theory and checking for consistency, (2) assessing the evidence for the theory, (3) scrutinizing alternative theories, and (4) testing the theories with the criteria of adequacy.