1. Chapter 10: Judging Scientific Theories
•The Scientific Method:
– 1. Identify the problem or pose a question.
– 2. Devise a hypothesis to explain the
event or phenomenon.
– 3. Derive a test implication or prediction.
– 4. Perform the test.
– 5. Accept or reject the hypothesis.

2. 1. Identify the problem or pose a
question
• The questions we ask are a reflection of our
interests. Science is not disinterested
knowledge accumulation – we are interested
in significant knowledge.
• What makes knowledge significant is that it is
knowledge that addresses our interests.
• What questions is the theory answering? Why
are we seeking knowledge?

3. 2. Devise a hypothesis to explain a
phenomenon.
• Where do hypotheses come from?
– Do we collect data and generalize from it –
enumerative induction? No!
– Hypotheses generally contain theoretical concepts
that are not in the observational data. Scientific
knowledge is not just generalization from
observation.
– Hypotheses also must be considered in relation to
alternatives – we never just look at one
hypothesis in isolation.

4. 3. Derive a test implication or
prediction.
• Typically scientific theories cannot be tested
directly (in part because they include
theoretical concepts that are not observable).
• We indirectly test a scientific hypothesis by
deriving observable test implications.

5. 4. Perform the test.
• If this hypothesis is true, what consequences
would follow?
If H, then C.
Not-C.
Therefore not-H.
• Deductive logic can disconfirm a hypothesis but
not confirm it. (Modus Tollens)
• But the process is rarely this simple – remember
we are testing hypotheses against each other and
not just against the observations.

6. 5. Accept or reject the hypothesis
• We cannot conclusively confirm a hypothesis
(ever). Thus accepting a hypothesis is always
provisional.
• This does not mean that all hypotheses are
equally good (or bad)! We have some (good)
reasons to prefer the better hypothesis.

7. Review: The Logic of Hypothesis Testing:
•The hypothesis disconfirmed—
– If H, then C.
– not-C.
– Therefore, not-H.
•The hypothesis confirmed—
– If H, then C.
– C.
– Therefore, H.
• This is not a valid deductive argument (affirming
the consequent) and so the reasoning here is
always provisional (inductive)

8. Judging Scientific Theories
• Testability: Whether there is some way to
determine if the theory is true (or false)
• Fruitfulness: The number of novel predictions
made
• Scope: The diversity of the phenomena
explained
• Simplicity: The number of assumptions made
• Conservatism: How well a theory fits with
existing knowledge

9. Making Weird Mistakes
• Leaping to the weirdest theory: Just because you can’t
think of a natural explanation does not mean that there
isn’t one.
• Mixing what seems with what is: just because something
seems real, it is real. (A better principle: It’s reasonable to
accept the evidence provided by personal experience
only if there’s no good reason to doubt it.)
• Misunderstanding the possibilities: confusing logical
possibility and physical possibility. Also, believing that if
something is logically possible, it must be actual.

10. • Common Mistakes in Assessing “Weird”
Theories:
 Believing that just because you can’t think of a
natural explanation, a phenomenon must be
paranormal.
 Thinking that just because something seems real, it
is real. (A better principle: It’s reasonable to accept
the evidence provided by personal experience only
if there’s no good reason to doubt it.)
 Misunderstanding logical possibility and physical
possibility. Also, believing that if something is
logically possible, it must be actual.