1. • When Claims Conflict
Contradictions - If a claim conflicts with
other claims we have good reason to
accept, we have good grounds for doubting
it.
If a claim conflicts with our background
information, we have good reason to doubt
it.
Chapter 4: Reasons for Belief and Doubt
2. Fact and Opinions
• Two meanings of “fact”
– State of affairs
– Claims that is true
• “That’s a matter of opinion”
– There are many different opinions about this issue
– There is no objective fact of the matter as the
grounds for deciding are entirely subjective
3. • Belief and Evidence
We should proportion our belief to the
evidence.
It’s not reasonable to believe a claim
when there is no good reason for doing
so.
4. • Experts and Evidence
If a claim conflicts with expert opinion,
we have good reason to doubt it.
Who is an expert?
Access to more information on the subject
than we do
They are better at judging that
information than we are.
5. When to rely on experts
• When they are experts in the relevant field
• When the are speaking or writing on their
subject of expertise
• When there is not some reason to doubt their
motivation
• When experts agree
6. • When the experts disagree about a claim, we
have good reason to doubt it.
7. Appeal to authority
• When any of the previous conditions is
violated the fallacy of appeal to authority is
committed.
• The reliance on expert opinion is undermined.
8. Some hints that the authority is dubious
• The expert is guilty of simple factual or formal errors.
• The expert’s claims conflict with what we have good
reason to believe.
• The expert does not adequately support his or her
assertions.
• The expert’s writing contains logical contradictions or
inconsistent statements
• The expert is strongly biased, emotional, or dismissive.
• The expert relies on information you know is out of date.
• The other experts in the same field disagree.
9. •Personal Experience
•It’s reasonable to accept the evidence
provided by personal experience only if
there’s no good reason to doubt it.
• Factors that can give us good reason to
doubt the reliability of personal experience:
Impairment
Expectation
Innumeracy
10. Impairment
• Memory
– We construct our memories
• Perception
– We sometimes see what we want to see – the
constructive nature of perception
11. Expectation
• Experiments showing that if we are told that
something is going to happen we will
experience it
• Pareidolia
• Stereotypes and perceptions:
racism/sexism/prejudice
12. Innumeracy
• We (humans) are bad at making judgments
about probabilities.
• We frequently make misjudgments about
coincidences.
• Gambler’s fallacy
So what conclusion should we draw from this?
Don’t rely solely on our intuitions.
16. Looking only for confirming evidence
• Confirmation bias
• Popper’s point about confirmation – what
makes a theory scientific
17. Preferring available evidence
• Availability error
– Not just what is readily available in the sense of
easy to find, but also what is psychologically
available.
– Weighting what you have seen or experienced
more heavily than it should be weighted
– Hasty generalization
18. • How to evaluate the reliability of
the news:
Consider whether the report conflicts
with what you have good reason to
believe.
Look for reporter slanting.
Consider the source.
Check for missing information.
Look for false emphasis.
Check alternative news sources.
19. Advertising and persuasion
• We generally have good reason to doubt
advertising claims and to be wary of
advertising’s persuasive powers.
– The purpose of advertising is to sell or promote
something.
– History of misleading messages
20. Identification
• Snob appeal
– Ads asking you to identify with particular groups
of people
– Insinuating that you will be identified with such
people if you….
22. Misleading comparisons
• Vagueness of comparisons
• What’s the baseline with which we are
comparing?
• Emptiness of claims
• Comparing “apples and oranges”
23.
24. Weasel words
• Words which appear to make a strong claim
but are really close to lying
• Taking back what was said with modifiers that
undermine the claim
