to the Best Explanation
Explanations (p. 294)
• Explanations answer the questions Why?
• The search for explanations often goes by
way of hypotheses.
• A. The hypothesis must have all the
properties for which you look in any
– 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
• No word should have more than one meaning as
employed in the explanation.
– 3. The hypothesis must be consistent; that is, the
hypothesis must not entail self-contradictory
– 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
– 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.
• 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
– 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
– This, of course, provides only inductive evidence that the
hypothesis is true.
• 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
– 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.)
– 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
– 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
– 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
• 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)
– 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
• 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
• 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
• Arguments to the best explanation always
involve two or more hypotheses.
– 1. Causal situations
– 2. Literary interpretation