Task 2 Flashcards
Logic
- Organized body of knowledge or science, that evaluates arguments
- Aim: to develop a system of methods/principles that we use as criteria for evaluating the arguments and to guide our own construction of arguments
- To distinguish good/bad arguments
Argument
-Group of statements (sentence that is either true or false)
truth value
two possible values for one statement (truth,falsity)
inference
- Reasoning process expressed by an argument
- Used interchangeably with ‘argument’
Proposition
-statement (meaning, info content)
2 conditions must be fulfilled for an argument
1) At least one of the statements must claim to present evidence or reasons
2) There must be a claim that the alleged evidence supports/implies smth (a claim that something follows from the alleged evidence/reasons)
noninferential passages (9)
1) warnings
2) piece of advice
3) statement of belief/opinion
4) loosely associated statements
5) reports (careful with reports about arguments!)
6) expository passages
7) illustrations
8) explanations
9) conditional statements
expository passages
- begins with topic sentence followed by one/more sentences that develop the topic sentence
- > try to find out if they try to prove that smth is true
Illustrations
- expression involving one/more examples
- to show what something means /how it is done
- often confused with arguments (uses indicator words such as ‘thus’)
- no claim that anything is being proved
- if claim illustrated is accepted by nearly everyone -> passage is no argument
explanations
- shed light on some event/phenomenon
- event in question is usually accepted as a matter of fact
- 2 components: explanadum (describes event/phenomenon), explanans (explaining)
- explains WHY smth is the case, does not prove THAT smth is the case
conditional statements
- if..(antecedent)…then( consequent)
- no claim to prove anything
- no single conditional statement is an argument , it can serve as premise or conclusion
1) Sufficient condition: A is all that is needed for occurrence of B
2) Necessary condition: Whenever A cannot occur without occurrence of B
Deducutive arguments (5)
- > Impossible for the conclusion to be false given that the premises are true
1) Argument based on mathematics (are all deductive, despite statistics)
2) Argument from definition
3) Categorical syllogism (each statement begins with one of the words ‘all’, ‘no’, or ‘some’)
4) Hypothetical syllogism (conditional statement in one or both premises)
5) Disjunctive syllogism (either..or)
Validity - deductive arguments
- Not determined by actual truth/falsity of premises and conclusion
- Determined by relationship (whether premises support conclusion)
- BUT: any deductive argument having actually true premises and actually false conclusion is invalid!
Valid -> impossible for the conclusion to be false, given the premises are true
Invalid -> possible for conclusion to be false -> conclusion does not follow with strict necessity from premises even though it is claimed to
soundness - deductive arguments
- Sound argument: deductive argument that is valid and has all true premises
- Unsound: invalid and one/more false premises
Inductive argument (6)
- Improbable that the conclusion be false given that the premises are true
1) Prediction (claim about future)
2) Argument from analogy
3) Generalization (use of stats)
4) Argument of authority
5) Argument based on signs (any kind of message (usually visual) produced by any intelligent being)
6) Causal inference (e.g. tasting a piece of chicken and finding it dry and tough, one might conclude that it had been overcooked)
Strength - inductive arguments
-Results not from actual truth/falsity but from probabilistic support the premises give to the conclusion
- Strong: improbable that conclusion is false given that premises are true
- Weak: conclusion does not follow probably from premises
Cogency - inductive arguments
- Cogent: inductive argument that is strong and has all true premises + premises meet the total evidence requirement
- Uncogent: weak/ has one or more false premises, fails to meet total evidence
Counterexample method
- A substitution instance having true premises and a false conclusion
- Used to prove invalidity of any invalid argument
- Cannot prove validity of any valid argument
- Useful to keep in mind terms ‘cats, dogs, mammals, fish and animals’ to use for counterexample
- Only for deductive arguments