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29 Cards in this Set

  • Front
  • Back
Proposition
• a true or false sentence
Argument
• a series of propositions the complete expression of which is divided into assumptions and conclusions by an inference indicator
Logical Contradiction
• any proposition that is never true, or that is false under any circumstances, no matter what the world happens to be like, or that is true just in case its negation is true
Logical Impossibility
• the truth of a proposition or the occurrence of a condition is logically impossible if and only if the proposition or the adequate description of the state of affairs it proposes involved a logical contradiction
Logical Necessity
• the truth of a proposition or the occurrence of a condition is logically necessary if and only if its falsehood or the nonoccurrence of the state of affairs it proposes is logically impossible
Deductively Valid Argument
• an argument that is such that it is logically necessary that id its assumptions are true, then its conclusions are true, or such that it is logically impossible for its assumptions to be true and its conclusions false
Sound Argument
• a deductively valid argument with only true assumptions
subject term
- subject of the proposition
- Alice is friendly.
predicate term
- the object of the proposition
- Alice is friendly
Copula
- Verb of the proposition
- Alice is friendly.
Assumption
- The ideas from which the conclusion are to follow
Conclusion
- The idea that is supposed to follow from the assumptions
inference indicator
- ‘thus,’ ‘hence,’ ‘therefore,’ etc.
reconstructed argument
1.) If the salmon are running then the river has melted
2.) But the river has not melted
3.) The salmon are not running
principle of charity
- Requires that whenever possible, we try to reconstruct arguments as deductively valid before criticizing their logical form or content
imagination test for deductive validity
Try to imagine the situation or set of circumstances in which the assumptions of an argument are true and the conclusions false. If you can do so, then there is a strong reason to believe that the argument is deductively invalid; if you cannot do so, then there is a strong reason to believe that the argument is deductively valid
conditional statement
‘if-then’ statement
antecedent
If P,
Consequent
Then Q
conditional argument
Contains at least one proposition that has an ‘if-then’ form
modus ponens
If P, then Q
P_______
Q
modus tollens
If P, then Q
Not Q_______
Not P
affirming the consequent
If P, then Q
Q_________
P
denying the antecedent
If P, then Q
Not P_______
Not Q
Contrapositive
If P, then Q
If not P, then not Q
hypothethical syllogism
If P, the Q
If Q, then R
If P, then R
disjunctive syllogism
P or Q
Not P
Q
constructive dilemma
P or Q
If P, then R
If Q, then R
R
reductio ad absurdum
P
Q_____
R and not R
Not-P