Lecture 4-what is an argument ? Validity or Truth 

by Marianne Talbot, university of Oxford 

 

We saw that, although we need to paraphrase arguments in order to complete these steps…..

We should not change the meaning of any of the premises or conclusion…..

 

We also saw that although it is necessary to bring to bear our understanding of the argument 

It is important not to read into the argument anything that isn’t there 

at least implicitly

 

It is extremely important in analyzing an argument, but not evaluate the argument

That comes later……

first we identify the argument then we evaluate it.

 

How to evaluate argument :

Starting with inductive arguments 

  “ Inductive arguments are such that…. 

     …. the truth of their premises….

     Makes the truth go their conclusion…..

                                 More or less likely….” 

 

All inductive arguments rely on the principle of the uniformity of nature….

And the only arguments for the principle of the uniformity of nature are themselves inductive.

…….a Circular…..

 

Types of inductive arguments :

1. Inductive generalizations

2. Causal generalizations

3. Arguments from analogy 

4. Arguments from authority 

 


 

1. Inductive generalizations

The premises identifies a characteristic of a sample of a population….

The conclusion extrapolates that characteristic to the rest of the population 

 

EX1 : 60% of the voters sampled said that they would vote for Mr. Many Promise 

      Therefore, Mr. Many Promise is likely to win.

 

EX2 :whenever I have try to ring BT it has taken me hours to get through.

     Therefore, when I ring BT today it will take hours to get through.

 

So which questions would you need to have answered in order to know whether or not these are good arguments ?

 

EX1: 

A: size (number) of sample

B: Mr. Many Promise is not a candidate            

C: range of ages 

D: region (complex)

E: occupation

F: who survey, radio, news, or party……(is the premises true?)

G: events happening (scandal / money laundry)

 

Is the premise true?

Can we really believe whoever claim that : (the party support Mr.MP)

Might they be bad at record-keeping ? (56% or 46% and not 60%) with exaggeration

Engaging in wishful thinking ? (being willing to vote Mr. MP)

Bad at math ? (60% ??)

 


 

EX2: 

A: Question the premise 

    When (2 in the morning, midnight…..)

    Hours??? 

    Maybe you are keen to someone to answer your phone immediately

B: times I call 

C: BT represent for ? 

    BT maybe have two different meaning ( franchises )

 

Is the premise true?

Am I telling the true when I say this (emotional)?

Am I in the pay of one go BT’s rivals ?

Am I prone to exaggeration ?

Am I bad at estimating time ?

 

Evaluation of arguments with 2 fundamental points :

1. Dose the conclusion follow from the premises 

2. Is the premise true ?

Fitting for any arguments (deductive or inductive)

 

How large is the sample ?

EX1: How many of those who would vote in the election were sampled ?

        10 out of 1 million ?

        1000 out of 1 million ?

EX2: how often have I rung BT in the past ?

         Once ?

         50 times ?

In the question of size, we cannot think about the accuracy of size, but we only can compare the size more or less

 

How representative is the sample ? 

EX1: were the voters sampled all female ?

        Over 40 years old ?

        White people ?

        Bourgeois ?

        Known to the person conducting the survey ?

 

In an election between Roosevelt and Landon :

They thought sixty of population was gonna vote the one their samples have said. 

But they find the samples by looking at the telephone books. 

In that period, there are very few telephones in families, so the samples were unrepresentative, because it was middle-glass people with fair amount of money who had telephones, and therefore it didn’t represent the population as a whole. 

Therefore, we have to cast the doubt on the census

 

EX2: have I only rung BT on Sunday ?

        When am I in hurry ?

        After 10 p.m.

 

Descartes, “The list of rule of thinking “ :

Take any problem you have

Then break it up into parts….

Dealing with each part separately…

Looking into each part you can put together as a solution to the whole 

Making sure your thoughts clearer.

Identify arguments analyze it evaluate it  

 

Beware ‘informal’ heuristics (rule of thumb—judgement from your experience)

EX1:

set1:

Three of clubs 

Seven of diamonds 

Nine of diamonds

Queen of hearts 

King of spades 

 

set2:

Ace of spades 

Ace of hearts

Ace of diamonds 

Ace of clubs 

King of spades 

 

Two sets of pokers above have the same proportion to come out 

But the survey of university students says the first situation would be more likely appeared than the second one. Because the first one you compared with is the pokers you seems likely to take many times before, but actually you did not take the same pokers as the 『set1』, just similar to the one you take. 

 

 

Beware ‘informal’ heuristics

EX2:

Set1:

In 4 pages of novel (2000words) 

how many words do you expect to find ending in “ing” ?

 

Set2:

In 4 pages of novel (2000words) 

how many words do you expect to find that include the letter “n”?

“n”s are more than “ing”s, because 『ING』 need to be bind together  without breaking apart. 

 

Comment: 

5 septs of Inductive generalizations (all inductive arguments can use these):

  1. Premise is true ?
  2. Is size of sampled population large enough compared to the population as a whole?
  3. Representative or bias ?
  4. Find counterexamples
  5. Get rid of informal heuristics!!!

NO.1 and NO.2 are very good standards for GRE when we examine the " strengthen " or " weaken " of the critical thinking 

 

2. Causal generalizations

The premise identifies correlation between two type of event….

The conclusion states the events of the first type cause events of the second type. 

 

Which questions would you need to have answered in order to know whether or not these are good arguments ?

EX1: Married men live longer than single men 

Therefore, being married causes men to live longer.

 

EX2: When air is allowed into a wound, maggots form.

Therefore, maggots in wounds are caused by air being allowed into the wound.

 

Is the premise true?

Who say married men live longer ?

Married men ?

 A woman who want to get married ?

 someone parents split up when someone was 5 ?

 

Who says maggots form when air gets into a wound ?

 A newly qualified nurse ?

 An elderly doctor ?

 A scientific study ?

 

We cannot determine causation if we find A cause B and try to find out why A cause B ?

our evidence of causation is always a correlation, but a correlation isn’t sufficient as evidence of causation 

 

EX: evidence of identity — 

1. evening stars go down, and sun rise.
They are the same regular thing, not caused by each other. 

2. do husbands cause wives ?
No. But they are correlative. 

 

John Mill—method of agreement and method of difference

What causes what ?

  1. They do correlate 
  2. try and bring about the cause without effect 
  3. Judge if there is sufficient for its cause and effect   

 

How strong is the correlation ?

EX1: How many married men were be observed ?

        Over how long ?

        Were unmarried men observed ?

EX2: how many cases of maggots forming were observed ?

        Were wounds into which air was not allowed observed ?

 

Make sense or Could it be accidental ?

Every time a match has been struck and a pineapple has fallen

EX1: why would being married cause men to live longer ?

EX2: Why would air getting into a wound cause maggots to form ?

 

What causes what ?

Could it be that being long-lived causes marriage in men ? ( reverse )

Could having the genes for longevity causes men to get married ?

 

Could maggots forming cause the air to get into a wound ?

Could there be something that causes both air getting into the wound and maggots to form ?

 

3.Argument from analogy 

Taking just one example of something 

and extrapolate from a character of that example

To the character of something similar to that thing  

 

EX: The universe is like a pocket watch 

      A pocket watch had a designer 

      Therefore the universe has a designer.

 

Evaluating :

Are the two similar ?

Are they similar to respect of something relevant ?

Can we find a dis analogy ?

 

4.Argument from authority 

Take one person or group of persons 

Who are, or are assumed to be, right about something

And extrapolate to the claim they are right about others.

EX:  

Human right monitoring organizations are experts on whether human right have been violated.

They say that some prisoners are mistreated in Mexico.

Therefore some prisoners are mistreated in Mexico.

 

Evaluating :

Who exactly is the source of information ?

Is this source qualified in the appropriate areas?

Is the source impartial in respect of this claim ?

Do other experts make other claims?

Find the answers, and you can evaluate whether the argument good or bad.


這裡開始進入能用在GRE考試的技巧了,除了上一講說到如何先釐清誰是前提誰是結論,所謂的logic book style,這裡第四講加上了,如何應付加強/削弱的題型,主要是掌握兩點,是否前提的句子『為真』,是否結論有『反例』

 

以上來自牛津大學教授上課筆記希望能幫上忙,喜歡,或是不喜歡還是有錯誤,歡迎留言指教,謝謝!! 

 


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