Transcript causal argument - David Kelsey`s Philosophy Home Page

Critical Thinking
Lecture 12
Causal Arguments
By David Kelsey
Causal Arguments
•
Causal claim: states or suggests the presence of causation.
– Examples:
•
A causal argument has as its conclusion a causal claim.
•
A cause is an event, person, place or thing X without which some other event,
person, place or thing Y, X’s effect, would not occur, exist, etc.
– A cause necessitates its effect such that without the cause, the effect would
not occur.
– Causes can’t just be correlations though.
• Causal powers
Post Hoc Fallacy
•
Post Hoc Fallacy: When one thinks that just because X is followed by Y this
must mean that X causes Y.
–
•
Post Hoc is short for Post Hoc, Ergo Propter Hoc which translates:
The mistake is Thinking Correlation entails causation:
–
Accidental correlation: this is a mistake because X could play no role in Y’s coming
to be.
• X could merely be accidentally correlated with the occurrence of Y.
• 3 pennies example:
• Other possibilities besides X causing Y or X and Y being accidentally correlated:
Hypotheses
•
Hypothesis: a supposition offered as a starting point for further investigation.
–
•
When hypothesizing you are conjecturing, I.e. making a guess about some way the
world is.
How do we test a hypothesis?
–
Look for counterexamples to it.
• What is a Counterexample?
• A counterexample to: Vitamin C cures colds
Relevant difference reasoning
•
Relevant difference reasoning:
– If some effect, Y, occurs in one situation & Y doesn’t occur in other
situations similar
– we can try to find something that is different about this situation, I.e. X.
– We then suspect this difference X is the cause of Y.
–
•
To find X, simply look for the differences between this situation and those situations
that are similar but in which Y doesn’t occur.
Use relevant difference reasoning when:
Which difference is relevant?
•
Question: how do you know which is the relevant difference?
– Engine overheating:
Examples of
Relevant difference reasoning
•
Examples of relevant difference reasoning:
– Headaches:
– Post Office:
Common Thread Reasoning
•
When do we use this kind of reasoning?
•
Look for a common thread: some event, person, place or thing that is
common to all the occurrences of the effect.
•
Mosquito example:
Common mistakes
in informal causal
reasoning
•
•
1.) We can overlook alternative common threads or differences:
–
If one difference or thread seems particularly relevant, don’t overlook others as you
may miss the real cause in doing so.
–
Example:
2.) We can focus on irrelevant differences or common threads:
–
To know that a difference or thread is relevant you must have some knowledge of the
situation, its causes and its effects.
3 more mistakes
•
3.) We can overlook the possibility that causation is the reverse of what has
been asserted:
–
•
4.) We can overlook the possibility that the asserted cause and effect are
both the effects of some third underlying cause:
–
•
Climbing a rope:
The leaves turning yellow:
5.) We can fail to consider the possibility of coincidence:
–
The cancer example:
Doubtful causal claims
•
1. Appeal to Anecdotal evidence: watch out for a causal claim when the
evidence is one or two cases only.
–
Smoking doesn’t cause cancer:
• To show smoking doesn’t cause cancer we need to show that even if everyone
smoked, the cancer rate would not increase. Can you do this with 1 piece of
evidence though?
•
2. Circularity: The cause cannot merely restate the effect for if so we haven’t
learned anything new.
–
•
Insomnia example:
3. Excessive Vagueness: if a causal claim is too vague we won’t know exactly
how it is to be tested.
–
Bad Karma example:
Doubtful causal
claims #2
•
4. Nontestability: we can’t have a causal claim for which testing is isn’t
possible.
–
•
5. Unnecessary assumptions: why needn’t make any unnecessary
assumptions in asserting a causal claim?
–
•
Aids example:
Déjà vu example:
6. Conflict with well-established theory: as a general rule, we don’t really
want our causal claims to conflict with our theories.
–
We can have theoretical advances, but…
–
Height example:
Causal Explanations
vs.
Arguments
•
A causal explanation is an explanation of the cause of something.
•
Explanations vs. Arguments: while causal explanations can look superficially
like arguments, explanations assert cause and effect while arguments try to
prove that something is the case.
•
Explaining causes: When we try to justify or defend or excuse something we or
someone else did, we sometimes explain its causes.
–
•
Bread example:
But not every attempt to explain behavior is an attempt to excuse it: One
might be simply trying to offer an explanation without any sympathy at all for the
actions being explained.
–
Nazi Germany example: