More Bad Reasoning
and
Bad Rhetoric
Violence to both People and Logic
Ad Hominem Fallacies
About persons instead of premises
Personal attack/favoritism
Inconsistency (incl. double standard)
Circumstantial (positive or negative)
Poisoning the well
Ad Hominem Fallacies
About persons instead of premises
Personal attack/favoritism
Inconsistency (incl. double standard)
Circumstantial (positive or negative)
Poisoning the well
Characteristics of the person are not irrelevant
when credibility of the source is an important factor
in determining whether a claim will be accepted.
Ad Hominem Fallacies
About persons instead of premises
Personal attack/favoritism
Inconsistency (incl. double standard)
Circumstantial (positive or negative)
Poisoning the well
Characteristics of the person are not irrelevant
when credibility of the source is an important factor
in determining whether a claim will be expected.
Genetic Fallacy
About origins of ideas instead of premises
Straw Man
Substituting a weak invention for reality
A strategy of refutation
Reworks some part of a case to make it
less viable
Uses exaggeration or oversimplification
to distort original position
The altered version of the original is
easier to refute than the original
False Dilemma
Treating contraries as contradictories
Occurs when a decision must be made
Limits alternatives (to two in a dilemma)
May use straw man technique to make one
alternative more attractive
May show up as “either-or” or “if-then”
False Dilemma
Treating contraries as contradictories
Occurs when a decision must be made
Limits alternatives (to two in a dilemma)
May use straw man technique to make one
alternative more attractive
May show up as “either-or” or “if-then”
May show up as perfectionist fallacy
(If it’s not perfect, then it’s not acceptable.)
False Dilemma
Treating contraries as contradictories
Occurs when a decision must be made
Limits alternatives (to two in a dilemma)
May use straw man technique to make one
alternative more attractive
May show up as “either-or” or “if-then”
May show up as perfectionist fallacy
(If it’s not perfect, then it’s not acceptable.)
May show up as line-drawing fallacy
(demand that category lines always be clear)
Slippery Slope
Misrepresenting probability and necessity
One version asserts in the manner of
inductive argument that some action will
inevitably (or almost certainly) lead to some
improbable consequence
Slippery Slope
Misrepresenting probability and necessity
One version asserts in the manner of
inductive argument that some action will
inevitably (or almost certainly) lead to some
improbable consequence
Second version asserts in the manner of a
justification or statement of principle that
once committed to a course of action, it
must be followed to its conclusion
Misplacing Burden of Proof
Appeal to Ignorance
An attempt to evade responsibility
Burden of proof: the requirement to supply
support for a claim
Misplacing Burden of Proof
Appeal to Ignorance
An attempt to evade responsibility
Burden of proof: the requirement to supply
support for a claim
Burden of proof shifts, depending on
conditions (lower initial plausibility,
affirmative more than negative, special
circumstances such as judicial “innocent
until proven guilty”)
Misplacing Burden of Proof
Appeal to Ignorance
An attempt to evade responsibility
Burden of proof: the requirement to supply
support for a claim
Burden of proof shifts, depending on
conditions (lower initial plausibility,
affirmative more than negative, special
circumstances such as judicial “innocent
until proven guilty”)
Problem may occur unexpectedly in debate
Begging the Question
Skipping over an important issue
May occur as a conclusion that restates a
premise
Begging the Question
Skipping over an important issue
May occur as a conclusion that restates a
premise
May occur as a premise controversial on
the same grounds as the conclusion
Begging the Question
Skipping over an important issue
May occur as a conclusion that restates a
premise
May occur as a premise controversial on
the same grounds as the conclusion
May occur as a premise that presupposes
the conclusion
Example: We need to widen this road because there aren’t
enough lanes to handle the traffic. (Begs the question of
whether all that traffic should or must be on that road.
Does not beg the question of how many lanes are needed.)