Critical Thinking:
Logical Reasoning and Argument

When reducing an argument to standard form, you attempt to clarify the argument by emphasizing its structure. Typically, this means converting an argument from paragraph form to a list of premises and conclusion (the therefore). The following is an example of a Syllogism, a major premise + a minor premise + a conclusion:

All professional athletes are paid far too much. Kevin Garnett is a professional basketball player, and he is definitely paid too much.

  • All professional athletes are paid too much.
  • Kevin Garnett is a professional athlete.
  • Kevin Garnett is paid too much.
What if the logic is sound, but one (or more) premise isn't?


Example:

The tragedy of HIV is that all who are infected with the virus face a premature death. Bob has been infected since 1996, and his life will be cut short as a result.

    • All people infected with HIV will die prematurely
    • Bob is infected with HIV.
    • Bob will die prematurely.

In its effort to improve its "public image," management at the Highland Hills Apartments has recently adopted a screening policy that allows them to refuse to rent to someone based solely on that person's criminal history. This policy is illegal and should be terminated.

  • An apartment manager's policy that denies rental opportunities to individuals with criminal histories is illegal and should be terminated.
  • The Highland Hills Apartments has a screening policy that denies rental opportunities to individuals with criminal histories.
  • The Highland Hills applicant screening policy is illegal and should be terminated.
Induction: Open Argument that Uses Inference: evidence 1 + evidence 2 + evidence n + conclusion

 
  • In a recent poll taken to measure the job approval rating of our governor, researchers found that Minnesotans are less pleased with the job performance of their governor after his first 100 days in office than they were after his first 30 days in office.
  • The same poll indicated that voters don't believe that Governor Ventura communicates well enough with legislative leaders.
  • A majority of participants in the poll cited Governor Ventura's apparent inability to ensure that the entire budget surplus from 1998 will in fact be returned to tax payers this year as their number one complaint regarding his job performance.
THEREFORE: We can conclude that Minnesotans want a governor who is willing to listen and cooperate with legislators as they draft laws and that gubernatorial candidates shouldn't make campaign promises they can't keep.
 

Deduction and The Conditional Argument:
If X then Y, X; therefore Y


 
  • If UConn does the seemingly impossible and wins the NCAA tournament, then I will win $80 in the English Department's tournament poll.
  • UConn did the seemingly impossible and won the NCAA tournament.
  • I won $80.


How conditional arguments can fail:
  • Failed Validity--desired CONSEQUENT isn't fulfilled.
  • Faulty conditions--your ANTECEDENT is bogus.
  • If adolescents view the movie The Basketball Diaries and play too many violent video games, then they will be inspired to go out and shoot people at random.
  • "Adolescent X" watched The Basketball Diaries and has played too many violent video games.
  • "Adolescent X" will be inspired to go out and shoot people at random.



PLAYING with Logical Argument Forms -
    Paragraph Form to Standard Form

Instructions: Convert each argument from paragraph form to standard form. Some paragraphs may have implied premises that will need to be made explicit in the standard form.

1. Deduction/Syllogism: Major Premise + Minor Premise + Conclusion
Problem: Is Bob an outstanding tennis player?

What makes Bob an outstanding tennis player is his repertoire of trick shots. Most tennis players donít use trick shots effectively, but outstanding players do, and Bob possesses an unusual number of trick shots. My favorite trick shot of his is the ultra-high lob he hits from between his legs when he is facing away from the net.

1.

2.
Therefore,
 

2.Deduction/Syllogism: Major Premise + Minor Premise + Conclusion
Problem: Our jails are full of people convicted of drug possession. How could one argue for decriminalizing drug possession?

Simple possession of illicit drugs should be decriminalized in America. Drug laws completely miss the mark in their effort to solve America's drug problem. Legislators don't realize that drug addicts are only hurting themselves when they use drugs, and it doesn't make sense to lock someone in prison unless their behavior hurts other people.

1.
2.
Therefore,

3. Induction: Evidence 1 + Evidence 2 + Evidence n + Conclusion

Problem:Why would the university care whether there are enough parking spots for students?

A business must keep its customers in order to remain successful, and customers may choose to do business elsewhere if a business does not provide parking spaces for them. Universities must provide parking spaces for students. If they don't, they may lose enrollment because students will go to schools where parking is not an issue.

1.
2.
3.
Therefore,

4. Deduction & The Conditional Argument:

Problem: How can the university create more parking spaces without creating new parking lots or ramps?

The University should encourage people to car pool in order to reduce demand on its limited parking space. The University could encourage people to car pool by charging parking rates based upon the number of occupants in the car; the more occupants, the lower the rate per hour. People will car pool because it saves each person money, and if more people car pool (as opposed to driving individually), fewer parking spots will be needed.

1.
2.
Therefore,