Deductive arguments Flashcards
What is a deductive argument?
An argument of such a form that if it’s premises are true, the conclusion must be true too
Modus ponens
If p, then q.
p.
Therefore, q.
Modus tollens
If p, then q.
Not-q.
Therefore, not-p.
Hypothetical syllogism
If p, then q.
If q, then r.
Therefore, if p then r.
What is q and p
q is the consequent, p is the antecedent
Disjunctive syllogism
p or q.
not-p.
therefore, q
Dilemma
p or q.
if p then r.
if q then s.
therefore, r or s
(hedgehog dilemma –> closer 2 hedgehogs get, the more likely they are to poke each other, but if they remain apart, they will be lonely. therefore, they suffer physically or emotionally)
Reductio ad absurdum
A version of modus tollens, means “reduction to absurdity”
Arguments by reductio establish their conclusions by showing that assuming the opposite leads to absurdity
- to prove: p
- assume the opposite: not-p
- Argue that from the assumption we’d have to conclude: q
- show that q is false (contradictory, ‘absurd’)
- conclude: p must be true after all
An argument of such a form that if it’s premises are true, the conclusion must be true too
What is a deductive argument?
If p, then q.
p.
Therefore, q.
Modus ponens
If p, then q.
Not-q.
Therefore, not-p.
Modus tollens
If p, then q.
If q, then r.
Therefore, if p then r.
Hypothetical syllogism
q is the consequent, p is the antecedent
What is q and p
p or q.
not-p.
therefore, q
Disjunctive syllogism
p or q.
if p then r.
if q then s.
therefore, r or s
(hedgehog dilemma –> closer 2 hedgehogs get, the more likely they are to poke each other, but if they remain apart, they will be lonely. therefore, they suffer physically or emotionally)
Dilemma
