Module 1: Intros Argument structure and basic reasoning Flashcards
argument components
an argument is made up of premises and a conclusion
Propositions
claims or parts of information building up an argument
- universal sentences
-propositions are broken down to premises and conclusions
Properties of propositions
-they have truth value
- they are shareable
- they are inter-translatable
Premises
The reasons presented to persuade someone that a conclusion is true or probably true
-are propositions that are used in support of the conclusion in a given argument
Conclusion
a judgement based on the information obtained through the premises
- proposition that sets out to prove in a given argument
Deductive reasoning
-from general to specific
-if all the premises are true then the conclusion must be true, aims to prove the conclusion with certainty
- a good deductive argument is both valid and sound
soundness
a valid argument where the premises are actually true
- relies on validity and refers to the content of the argument specifically the truth of the premises
- if an argument is sound then the conclusion is true
an argument can be
- valid and sound
- valid but unsound
- invalid and unsound
arguments cannot be invalid but sound, true or false
truth preserving
a characteristic of a valid deductive argument in which the logical structure guarantees the truth of the conclusion if the premises are true
inductive reasoning
specific to general
- aim to show that the conclusion is probably true
- can be strong and cogent
Example of deductive reasoning
-all cats are born with nine lives
-Felix is a cat
-Therefore Felix was born with 9 lives
Example of inductive reasoning
-Every time I have walked by that dog, he hasn’t tried to bite me
-so the next time I walk by that dog he wont try to bite me
Strength
an argument is strong hen the premises are true which means that the conclusion is probably true
- corresponds with validity
Cogency
is a strong argument which has true premises
- corresponds with soundness
types of valid arguments
- Modus Ponens
- Modus Tollens
- Hypothetical Syllogism
- Disjunctive Syllogism
- Reducitio ad absurdum
- Modus Tollens
-Denying the consequent (then clause)
if P then Q
not Q
therefore not P
-valid and sound
types of invalid arguments
- Affirming the consequent
- Denying the antecedent
- Disjunctive Fallacy
- Ad Hominem
- Strawman Fallacy
- Appeal to Authority
- False Dilemma or False dichotomy
- Slippery slope fallacy
- Begging the question
- Equivocation
- Post hoc ergo Propter hoc
Disjunctive Fallacy
either P or Q
not P
therefore not Q
INCLUSIVE OR
1. I will have a sandwich or a cup of coffee after work
2. I will have a sandwich after work
3. Therefore i wont have a cup of coffee after work
-invalid and unsound
Disjunctive Syllogism
either P or Q
not P
therefore Q
EXCLUSIVE OR
- Serena or Venus won the tennis match
- Serena won the match
- Therefore Venus did not win the match
Hypothetical Syllogism
if P then Q
if Q then R
therefore if P then R
- Either there is tea in my mug or there is coffee in my mug
- There is not tea in my mug
- Therefore there is coffee in my mug
-valid and sound
Reductio ad absurdum
kind of reasoning where you accept some hypothesis for the sake of argument and then you show that the hypothesis leads to a contradiction. The arguer assumes the opposite of the conclusion they want to prove to show that it leads to a contradiction
If P then Q, not Q therefore not P
Fallacy
a mistaken belief especially one based on an unsound argument
Consequent
last half of a hypothetical proposition whenever the if clause precedes the then clause
Antecedent
first half of a hypothetical proposition whenever the if clause precedes the then clause
Affirming the consequent
if P then Q
Q
therefore P
if its raining then the grass is wet; the grass is wet therefore it is raining
- invalid and unsound
Denying the antecedent
if P then Q
not P
therefore not Q
if its raining then the grass is wet; its not raining therefore the grass is not wet
-invalid and unsound
Post hoc ergo propter hoc- Fallacy
P came before Q
P caused Q
Soundness
when a deductive argument is valid and all the premises are actually true
Strength of inductive arguments
Inductive arguments are not truth preserving they can be more or less strong depending on the premises
Cogency
an inductive argument which has true premises and good reasoning
Equivocation
using the same term with different meanings
appeal to authority fallacy
error of accepting a claim merely because an authority figure endorses it
Straw man Fallacy
Misrepresenting someones argument to make it easier to attack
valid argument definition
an argument is deductively valid if the conclusion is entailed by or logically follows from the premises
invalid argument definition
is a deductive argument that fails to have its conclusion logically follow from the premises
Modus Ponens
-Affirming the antecedent (if clause)
- if P then Q, P therefore Q
- if its raining then the grass is wet; it is raining therefore the grass is wet
-P2: false because the grass might be wet from something else
- valid and unsound
false dilemma
when the options of an argument do not exhaust the relevant possibilities
arguments by analogy
arguments that are hostage to the discovery of unnoticed disanalgies
begging the question
assuming the point at issue in attempting to argue for it
