Phil 145, Week 4

4a Biasing through exaggerated social support.

False consensus effect

People's own beliefs, values, and habits tend to bias their estimates of how widely such views and habits are shared by others. Everyone thinks like me? People read only material that agrees with them.

This is encouraged by the reluctance of people to express disagreements and criticisms. Contrast children, old people with Alzheimers.

Connects with other error tendencies, e.g. motivated inference (you want people to agree with you) and confirmation bias (you only associate with people who agree with youi).


We're doing ok. E.g. Harris cabinet and environment. First draft of Induction.

Cognitive process: make our beliefs cohere with those of others.

Motivation: fit in with group.

How to avoid groupthink:

Pluralistic ignorance.

In class, nobody asks questions, so each student thinks that all the other students know what's going on.

Students think other students are more keen on drinking than they really are, so they see it as more socially necessary. Similarly for sexual behavior.

Two people may both sit through a movie they hate, not realizing that the other hates the movie too.

Results from lack of data and biased data.

This is the opposite of false consensus (everyone is like me): with pluralistic ignorance (everyone is different from me), people underestimate the extent of agreement.

Error tendencies

False consensus (Gilovich, ch. 7)

Tendency to overestimate the extent to which other people agree with you

Groupthink (Gilovich, ch. 7)

Tendency for people working in groups to reach uncritical conclusions.

Pluralistic ignorance (not in text)

Tendency not to realize that other people have beliefs similar to yours.

4b Knowledge, belief, and evidence

Theories of knowledge

Knowledge is justified true belief.

Skepticism: we don't know anything

Relativism: knowledge is not objective, but is relative to individuals or social groups (see Schick, ch. 4)

Empiricism: knowledge comes from sense experience

Rationalism: knowledge comes from pure reason

Explanationism: knowledge is based on inference to the best explanation.

Coherence and introspection are useful, but can be misleading.

Reasoning strategy:

Inference to the best explanation

The competing hypotheses are H1, H2 ...

The available evidence is E1, E2, ...

Hypothesis H1 is a better explanation of the evidence than the other hypotheses, because:

It explains more evidence.

It is simpler, i.e. requires fewer extra assumptions.

It fits better with the rest of what we believe.

Therefore, we are justified in believing H1.


Why did the dinosaurs become extinct?

Who killed OJ's ex-wife?

Why did the professor not show up for class?

Expert opinion

Often we have to rely on what experts tell us.

But experts are not always right, especially when experts disagree.

If experts do agree, we have reason to doubt what conflicts with them.

Beware of experts speaking outside their areas of expertise, e.g. actors endorsing medical treatments.

Beware of experts' overconfidence (contrast Russell).


Faith = believing something that does not rest on proof or evidence.

Faith in someone, i.e. confidence, can be based on evidence.

If religious faith is a good thinking strategy, which religion should you have faith in?

Is believing on faith a kind of motivated inference?

Note: religious belief does not have to be based on faith. The existence of God can be defended by inference to the best explanation.


Intuition = believing something based on a feeling or "sixth sense."

Intuition can sometimes be reliable, if it is based on unconscious reasoning and evidence. E.g. an entrepreneur's gut feeling.

But intuition can also be arbitrary and erroneous, if based on poor evidence and motivated inference.

Mystical experience

Mystical experience = direct experience of reality that transcends sensory perception and reasoning.

Are mystical experiences hallucinations? What other explanations of reports of mystical experiences are available?

Error tendencies

Bogus authority (Schick, ch. 5, and p. 288)

Tendency to believe authorities when they are speaking outside their areas of expertise.

Intuition (Schick, ch. 5)

Tendency to form beliefs based on a feeling or sixth sense, without evaluation of evidence.

Mystical experience (Schick, ch. 5)

Tendency to form beliefs on the basis of an ineffable, personal, direct experience of reality.

Updated Jan. 27, 2003

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