This document discusses the scientific method and criteria for judging scientific theories. It outlines the key steps of the scientific method as: 1) identifying a problem or question, 2) devising a hypothesis, 3) deriving a test implication, 4) performing a test, and 5) accepting or rejecting the hypothesis. Additional criteria for judging theories discussed include testability, fruitfulness, scope, simplicity, and conservatism. Common mistakes in assessing "weird" theories are also summarized, such as leaping to strange conclusions without considering natural explanations or confusing what seems possible with what is actually possible.

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.