Chapter 27:Hypotheses, Explanations,

and Inference to the Best Explanation

Explanations (p. 294)

• Explanations answer the questions Why? or How?

• The search for explanations often goes by way of hypotheses.

Evaluating Hypotheses (pp. 294-299)

• A. The hypothesis must have all the properties for which you look in any discourse:– 1. The hypothesis must not merely redescribe

the phenomenon in different words.• The “phenomenon” is the event to be explained. It

might be a physical phenomenon, the behavior of a person, etc.

– 2. The hypothesis must be free from ambiguities.

• No word should have more than one meaning as employed in the explanation.

Evaluating Hypotheses (pp. 294-299)

– 3. The hypothesis must be consistent; that is, the hypothesis must not entail self-contradictory statements.

– 4. The hypothesis and predictions made on the basis of the hypothesis must be precise.

• B. Hypotheses explain phenomena and provide the basis for predictions and retrodictions.– Predictions concern events in the future.– Retrodictions concern events in the past. If a

retrodiction is correct, it might help you uncover some unnoticed historical event, for example.

Evaluating Hypotheses (pp. 294-299)

• C. Criteria for evaluating hypotheses– 1. A hypothesis must be testable.

• There must be a procedure for determining whether the predictions (retrodictions) proposed by the hypothesis can be realized.

– 2. If predictions based upon a hypothesis are true, this tends to show that that the hypothesis is true.

• a. Confirming a hypothesis and the argument form affirming the consequent.

– This, of course, provides only inductive evidence that the hypothesis is true.

Evaluating Hypotheses (pp. 294-299)

• b. Falsifying a hypothesis and denying the consequent– This provides conclusive evidence that either the hypothesis or some

unstated assumption (part of a more general theory, for example) is false.

– In practice, well-confirmed hypotheses might not be rejected until there is an alternative hypothesis that explains both the anomalous phenomenon and why the original hypothesis failed. While certain predictions based on Newton’s Theory were proven false in the mid-nineteenth century, Newton’s Theory remained in use until it was supplanted by Einstein’s Theory, which explained both the anomalous phenomena and determined the limits of Newton’s Theory. (Newton’s Theory works very well for “middle-sized” objects: larger than subatomic particles and smaller than galactic systems.)

Evaluating Hypotheses (pp. 294-299)

– 3. A hypothesis is more probably true if it has a broader explanatory scope, that is, if it explains more phenomena than alternative hypotheses.

• Consilience is the tendency of several forms of inductive evidence to point to the same conclusion.

• Explanatory scope is the class of phenomena a hypothesis will explain.

– 4. If either of two hypotheses will explain a phenomena and one involves fewer theoretical assumptions, the hypothesis that involves fewer assumptions is more probably true.

• Simplicity: The hypothesis with fewer theoretical assumptions is said to be the simpler hypothesis.

• The Principle of Parsimony or Ockham’s Razor (named after the 13th century English philosopher William of Ockham) is the principle that the theoretically simplest theory is most probably true.

Evaluating Hypotheses (pp. 294-299)

– 5. A hypothesis is more probably true if it is consistent with the best theoretical explanations available.

• 1. The theory guides you regarding what are probably relevant hypotheses.

• 2. Theories explain.• 3. Theoretical explanations are conservative.

– Novel explanations must be shown superior to explanations that are already accepted.

– 6. A hypothesis is more probably true if it is fruitful, that is, if it predicts previously unknown phenomena.

• The first five criteria apply to cases of troubleshooting as well as scientific hypotheses. This one is concerned primarily with the acceptance of broader theories, that is, scientific and historical theories, for example.

Examples (pp. 300-308)

• Troubleshooting– Consider the procedures you undertake in trying to

figure out why an ordinary, everyday thing isn’t working properly. Why won’t your car start? Why does water periodically flow into the tank of your toilet? Why does your InkJet printer smear the ink?

• B. Theories– An explanatory theory consists of a number of well-

confirmed, interrelated hypotheses that explain a phenomenon of a certain kind.

– 1. The crash of Stardust– 2. Madam Curie and the discovery or radium

Examples (pp. 300-308)

• a. Internal consistency – A theory, or any other kind of discourse, is internally

consistent if and only if there are not two or more propositions that can be combined to form a contradiction.

• b. External consistency– In the sciences, external consistency is the consistency

between claims made by a hypothesis for which there appears to be evidence and the ongoing theoretical assumptions of a science.

– 3. Barry Marshall and the cause of ulcers– 4. Barbara McClintock

Arguments to the best explanation (pp. 300-308)

• The best explanation is that which is so judged on the basis of the criteria for evaluating hypotheses. For example, if you have two hypotheses and one hypothesis is theoretically simpler than the other, then, all things being equal on the basis of the other criteria, the theoretically simpler hypothesis provides the better explanation.

• Arguments to the best explanation always involve two or more hypotheses.– 1. Causal situations– 2. Literary interpretation