Critical Thinking Misc. Flashcards
Simple sentences contain…
One assertion
Compound sentences contain…
Two or more assertions
Conjunction examples:
‘and’, semi-colon, ‘while’, ‘but’, ‘although’
Argument definition (lecture):
A discourse in which some statements are offered as justifying, proving or making probable some other statement
Modal expressions examples:
‘must’, ‘possibly’, ‘may’, ‘can’, ‘probably’
How modal expressions are used:
Necessary truths or necessary falsehoods, capacities and opportunities, inference indicators
Necessary truth:
Things that can’t be false by definition
Contingent truth:
A true statement which is, as a matter of fact, true, but could possibly have been false
Two ways in which a statement can be derived from two other statements:
Convergent and linked
Convergent structure:
When a conclusion can be derived from each premise of them quite independently of its derivation from the other.
Linked structure:
When a statement can be derived only by taking the two statements together, each of them on its own giving no independent support to the conclusion but giving some support when combined.
Assessing support question:
‘Supposing for the sake of argument that these premises are true, how improbable does this make it that the conclusion is false?’ In the case where “if the premises were true it would be impossible for the conclusion to be false” we have complete support.
Deductive validity:
The truth of the premises’ guaranteeing absolutely the truth of the conclusion
Test for validity:
(1) Drop the inference indicator
(2) Conjoin (&) premises and negation of conclusion
(3) If result is a contradiction, argument is valid
Estimating degrees of support question:
Supposing the premise(s) were true, is there any way not involving contradiction in which the conclusion nevertheless would be false? If there is no way, then the degree of support is complete.
Formal Logic (deductively valid):
All C are M
All M are H
Therefore,
All C are H
Disjunctive syllogism:
Either P or Q; but not-P; so, Q
A priori truth:
A claim which can be shown to be true or false without having to look at the world to find out.
A priori truths are contrasted with…
A posteriori claims
A cogent argument:
An argument in which the premises are rationally acceptable and also strongly support the conclusion
Transposition (deductively valid):
If A then B = If not-B then not-A
Double negation:
A = not-not-A
Sufficient vs Necessity:
The antecedent is sufficient for the consequent, and the consequent is necessary for the antecedent.
Only if:
If P then Q = P only if Q
Unless:
If P then Q = Not-P unless Q
Biconditional form:
If P then Q = P if and only if Q
Hypothetical syllogism (valid)
If A then B
If B then C
Therefore,
If A then C
Modus Ponens (valid):
If A, then C
A
Therefore,
C
Modus Tollens (valid):
If A, then C
Not-C
Therefore
Not-A
Denying the antecedent (invalid):
If A, then C
Not-A
Therefore,
Not-C
Affirming the consequent (invalid):
If A, then C
C,
Therefore,
A
Conditionalisation (not equivalent, they correspond)
P, so C = If P then C
Broad reductio:
Produces a consequence that is thought to be absurd because it is obviously false. This doesn’t have to be a contradiction.
Narrow Reductio:
Produces an explicit contradiction
