Reason & ArgumentLecture 5

Coursework Assignment

Will be released automatically on MOLE, first thing on Monday the 12th of November.

Consists of two sections - you must do BOTH.

One section requires you to identify a particular type of argument in a real-world source (e.g. a newspaper or web-site)

The other section requires you to construct arguments of your own to meet various criteria.

Lecture Synopsis

• POP QUIZ!

• How much do you really know about what we’ve learned so far?

• This quiz should help you to consolidate your knowledge & help you identify any gaps or weaknesses.

What You’ve Learned

In theory you can all now do the following:

Identify an argument, identify its premises & conclusion.

Reconstruct an argument, even when it is not fully explicit.

Determine whether an argument is valid and/or sound.

Identify common syllogisms & fallacies.

Argue effectively (and validly) for a ‘should’ conclusion.

Identify indexicals, predicates, vagueness, 3 types of ambiguity, and equivocation.

Pop Quiz

Can you do it in practice?

Identifying valid arguments

Identifying tacit/implicit premises

Identifying common syllogisms/fallacies

Constructing ‘should’ arguments

Identifying & Resolving ambiguities

Real-world Scenario

Imagine you are the CEO of a large company.

You are presented with a report by your Human Resources/Personnel division about the company’s employees, consultants and information about the Trade Union.

You must approve the report as containing accurate information & valid/sound arguments.

The information in the report will be vital for various decisions: raising/lowering pay, hiring/firing staff, etc.

Identifying valid arguments

• “All employees have degrees, and all consultants have degrees. So at least some employees must be consultants.”

Argument?

Yes.

Conclusion?

‘at least some employees must be consultants.’

Valid?

No.

Identifying valid arguments

• “All new employees have degrees, but all consultants have degrees. Also, since 1990, none of our employees has been a consultant.”

Argument?

No. (N.B. no premise or conclusion indicators)

Identifying valid arguments

• “Since all our employees have degrees, and anyone who has a degree has attended school, all our employees must have attended school.”

Argument?

Yes.

Conclusion

‘ [So] all our employees must have attended school.’

Valid?

Yes.

Identifying valid arguments

• “Every employee is a member of the Union. Every member of the Union has a right to strike. So every employee must have a right to strike.”

Argument?

Yes.

Conclusion?

‘every employee must have a right to strike.’

Valid?

Yes.

Identifying valid arguments

• “Not all employees work overtime. Some consultants are part-time. But every employee who works overtime is part-time.”

Argument?

No.

Identifying valid arguments

• “If employees stage a strike, then company profits will decrease. Company profits have decreased. So employees must be staging a strike.”

Argument?

Yes.

Conclusion?

‘employees must be staging a strike’

Valid?

No.

Tacit/Implicit Premises

What is a tacit premise?

A premise that is unstated, but which is needed to make the argument valid.

Can you identify the tacit premises in the following arguments from our fictional HR report?

Tacit Premises

• “Part-time employees have higher rates of sick leave than full-time employees. So part-time employees are not as dedicated to their jobs as full-time employees.”

Tacit premise?

Employees with higher rates of sick leave are not as dedicated to their jobs as those with normal rates of sick leave.

Tacit Premises

• “Employees hired on fixed term contracts cannot join the pension scheme. So the last 8 employees hired cannot join the pension scheme.”

Tacit premise?

The last 8 employees hired are on fixed term contracts.

Tacit Premises

• “If company profits increase, then our employees must be working hard. Company profits have increased. So our employees deserve pay rises.”

Tacit sub-conclusion?

So our employees must be working hard.

Tacit premise?

Employees who work hard deserve pay rises.

Syllogisms/Fallacies

Remember this argument?

• “If employees stage a strike [If X], then company profits will decrease [then Y]. Company profits have decreased [Y]. So employees must be staging a strike. [So X]”

This argument is an example of a fallacy.

What is a fallacy?

A pattern of reasoning that is always invalid.

But which fallacy?

Affirming the consequent (If X, then Y; Y; So X)

Syllogisms/Fallacies

•“If Union members object to the pay cut, then the Union will lodge a complaint. The Union has not lodged a complaint. So Union members do not object to the pay cut.”

This is an example of a syllogism:

What is a syllogism?

A pattern of reasoning that is always valid (at least, according to Aristotle).

Which syllogism?

Modus Tollens (If X, then Y; Not-Y; So not-X)

Syllogisms/Fallacies

•“If all employees join the Union, then the Union will grow stronger. If the Union grows stronger, cutting pay will be more difficult. So if all employees join the Union, cutting pay will be more difficult.”

Valid?

Yes.

Is it a syllogism?

Yes!

Which one?

Hypothetical Syllogism (If X, then Y; If Y, then Z; So if X, then Z)

Syllogisms/Fallacies

“If the Union agrees to the pension deal, then we can raise salaries. The Union does not agree to the pension deal. So we cannot raise salaries.”

Valid?

No!

Is it a fallacy?

Yes.

Which one?

Denying the antecedent (If X, then Y; Not-X; So not-Y)

Syllogisms/Fallacies

• “If the Union agrees, then we can raise salaries. The Union agrees. So we can raise salaries.”

Valid?

Yes!

Which syllogism?

Modus Ponens (If X, then Y; X; So Y)

Syllogisms/Fallacies

“If all our employees join the pension fund, the fund will collapse. The fund has collapsed. So all our employees joined the pension fund.”

Valid?

No!

Which fallacy?

Affirming the consequent(again) (If X, then Y; Y; So X)

Constructing Should Arguments

What are the components of a successful & valid ‘should’ argument?

Success Condition (SC)

P’s doing x will achieve y.

Optimal Means Condition (OMC)

x is the best way of P’s achieving y.

Ends-Justify-Means (EJM)

All things considered, P’s doing x and achieving y is better than P’s not doing so.

Example

Conclusion: The company should hire more employees.

SC: Hiring more employees will increase company profits.

OMC: Hiring more employees is the best way to increase company profits.

EJM: All things considered, hiring more employees and increasing company profits is better than not doing so.

(If SC, OMC, EJM, then the company should hire more employees)

Ambiguity

Lexical

A word in the sentence has two or more meanings.

Syntactic

The sentence structure allows for two or more different interpretations of its meaning.

Contextual

The context allows for different interpretations of the meaning of a sentence. Examples?

Indexicals (I, he, she, them, yesterday, etc.)

Comparison Classes (healthier, smarter, better, bigger, etc.)

Quantifier Omission (all, most, some, both, one, etc.)

Ambiguities

SAFETY EXPERTS SAY SCHOOL BUS PASSENGERS SHOULD BE BELTED

Lexical (‘belted’)

STOLEN PAINTING FOUND BY TREE

Syntactic (found beside vs. found by)

Ambiguities

MINERS REFUSE TO WORK AFTER DEATH

Syntactic (work after death)

PROSTITUTES APPEAL TO POPE

Lexical (‘appeal’: entreaty vs. attract)

KIDS MAKE NUTRITIOUS SNACKS

Lexical (‘make’)

Equivocation

What is equivocation?

The use of ambiguous words or syntax to conceal the truth or avoid committing oneself.

•Hot dogs are better than nothing

•Nothing is better than steak.

•Therefore, hot dogs are better than steak.

Where is the ambiguity?

‘nothing’: (1) no food at all vs. (2) no other food.

Equivocation

A less frivolous example:

•We are told that discrimination is morally wrong. But we always praise people for being discriminating in their taste for good wine, books or friends. So if I discriminate against women when they apply for jobs in my department, I will be praised for it.

Lexical - ‘Discrimination’ - (1) being able to detect subtle differences in the quality of things (2) treating people differently on the basis of arbitrary characterisitcs (sex/gender, race, religion, etc.)

Dealing with Equivocation

Phase 1:

Identify the word or phrase with multiple meanings.

Phase 2:

Eliminate the word & replace it with a phrase that clearly expresses *one* of the meanings. Note how the argument fails. AND/OR

Replace the word with a phrase expressing the other meaning, and note how it still fails.

Equivocation

We are told that treating people differently on the basis of their sex, race or religious beliefs is morally wrong. But we always praise people for treating people like this. So if I discriminate against women when they apply for jobs in my department, I will be praised for it.

OR:

We are told that being able to detect subtle differences in the quality of things is morally wrong. But we always praise people for being able to detect subtle difference in the quality of wine, books or friends. So if I am able to detect subtle differences in the quality of women when they apply for jobs in my department, I will be praised for it.