Evolution and Logical Fallacies
Christians have moral obligation to be rational
Both evolutionists and creationists make logical fallacies
Proposition – a statement that affirms or denies something and is either true or false
Commands – not affirming nor questions
Argument – a group of propositions where the truth of one is claimed to follow from the others
1. All mammals have kidneys (premise)
2. All dogs are mammals (premise)
3. Therefore, all dogs have kidneys(conclusion)
Deductive syllogism (2 premises and 1 conclusion)
Logical fallacy – a common error in the “chain of reasoning” ie conclusion does not follow the premises
1. Some mammals are cats
2. All dogs are mammals
3. Therefore, some dogs are cats
Fallacies are persuasive
Validity
An argument is valid if the conclusion does follow from the premises
An argument is invalid if the conclusion does not follow form the premises
1. All mammals are reptiles
2. All dogs are mammals
3. Therefore, all dogs are reptiles
It is valid; conclusion does follow from the premises
Err in chain of reasoning, or a false premise/ Valid does not mean it is good just sound
Soundness
An argument is sound if it is valid and if the premises are true. In a sound argument, the conclusion
must be true
If an argument is unsound, then the conclusion is unreliable
Is the argument valid? Is it sound?
1. All mammals have kidneys
2. All dogs are mammals
3. Therefore, all dogs have kidney
Yes, Yes
1. All mammals are reptiles
2. All dogs are mammals
3. Therefore, all dogs are reptiles
Yes, No
Deductive (formal) argument: The conclusion is definitely true if the premises are(if p then q)
Inductive (informal) argument: The conclusion is likely to be true if the premises are
An inductive argument is probabilistic in nature. Additional information can change a strong argument
to a weak one
Informal (ordinary language) Fallacies
1. Fallacies of ambiguity – unclear and vague
a. Equivocation – shifting the meaning of a word within an argument (bait and switch)
- Practice makes perfect, Doctors practice medicine, therefore doctors are perfect
b. reification – attributing concrete(and often personal) characteristics to an abstraction,
nothing wrong with it – proverbs does it, but in an argument
- Evolution figured out a way around these problems
2. Fallacies of presumptions - unwarranted
a. Sweeping generalization
b. Hasty generalization
c. Bifurcation – (false dilemma, the either or fallacy) – falsely assuming that there are only
two (exclusive) options.
- Either the traffic light is red, or it is green (what about yellow?)
d. Begging the question – circular reasoning – where the conclusion of an argument is
incorporated into the premises or a premise depends upon the conclusion
o It’s unusual because it’s valid, it’s assuming so it’s arbitrary
e. Question begging epithet – using biased language to support a conclusion that is
logically unproved
- Subtle – Evolution vs creationism… attaching ism means it’s a belief
f. Complex question – phrasing a question such that it assumes a conclusion
g. No true Scotsman – protecting a claim from counter-argument by defining a term in a
biased way
3. Fallacies of relevance
a. Genetic fallacy
b. Abusive ad hominem – when an argument is directed against a person rather than his or
her position
“joe is a mean person, so I wouldn’t believe anything he says
c. Circumstantial ad hominem – claiming that an argument is only due to a person’s
circumstances
- You’re only Christian because you were raised in a Christian home
d. Straw man – an argument that is against the misrepresentation of the opponent’s
position rather than the actual position
e. Irrelevant thesis –when an argument proves a point that is not an issue
f. Faulty appeals – when a person appeals to something or someone in a wy that is not
relevant to the claim
-
To appeal to the Bible… experts can be wrong, but God cannot be – not a fallacy
g. Ignorance - There must be life in outer space, no one has ever proved that there is not
For every arbitrary claim, there is an equal and opposite arbitrary claim
Deductive claim
Categorical
-
All
Some
No
Not
Propositional
if-then
and
or
not
Mixed hypothetical syllogism
If p then q (p – antecedent) (q- is called the consequent)
Fallacy of affirming the consequent
Fallacy of denying the antecedent
Valid: Modus Ponens no fallacy, false premise
Necessity of Consistency – from two contradictory premises, I can validly conclude absolutely anything
-
1, Dr x is teaching a class on apologetics (assume 1 and 2 is true)
2. Dr x is not teaching a class on apologetics
3. Either dr x is teaching a class on apologetics, or the mood is made of green cheese
Dr x is not teaching a class on apologetics (2)
Therefore, the moon is made of green chee