MODR 1730 Lecture Notes - Lecture 8: Presupposition, Argument Principle, Fallacy
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Lecture Eight: Fallacies Part Two
November 9, 2011
Fallacy Six: Self-Evident Truth
Definition - This fallacy is committed when the arguer presents their argument as self-
evident (“everybody already knows...”), and therefore does not need to prove it.
This fallacy violates both the argument principle and the reason principle.
It implies that whoever does not believe the argument, or who does not agree that it is
self-evident isn’t intelligent or is deficient in some other way.
“Women should not be in decision-making positions. Isn’t it obvious that they are more
emotional than men? And since women are more emotional, they are likely to make
decisions based on emotions rather than reasons”
The indicator phrase in this example is “Isn’t it obvious...”.
-It implies that the person being argued to should already believe to be true what the
arguer is presenting to them
-It also implies that the conclusion is self-evident, meaning that there is no need for
them to further prove their statements because it is obvious
-If the arguer provides a reason for why they have come to the conclusion, then this
fallacy is not committed
Fallacy Seven: Appeal to Ignorance
Definition: This fallacy is committed when an opponents inability to prove something is
used as proof to justify the arguer’s conclusion.
There are two types of this fallacy
-If you can’t prove it’s right, then it’s wrong
-If you can’t prove its wrong, then it must be right
This is a fallacy because the whole argument is based on a lack of evidence, instead of
using evidence to support the conclusion.
-The fact that there is no evidence to the contrary is used as justification for the