Logical arguments, Part I

  1. Basic format & terms

A+B=C

C= Conclusion, or for your paper your Thesis. You are trying to give two facts that logically prove your Thesis to be true.

A= first fact is called your Major Premise.

B= second fact is called your Minor Premise.

A= “All birds are animals”

B= Ducks are birdsGeneral to specific = Deductive

C= Ducks are animalsDeductive easier to prove definitely.

A= Gilly is a spaceman

B= Gilly drives a spacecraftSpecific to General= Inductive

C= Some Spacemen drive spacecraftsRequires qualifiers to be true.

A = The postman has always delivered mail by 2pm

B= Postman is scheduled to deliver mail today.Based on consistent data=Abductive

C= The postman will probably deliver mail by 2pm todayOnly possible to prove probably – Strong or weak(type of inductive argument)

You CAN compress a syllogism (Enthymeme) – uses the word ‘because’

“Ducks are animals because they are birds” – This is likely how you have your Thesis currently

(That was an inductive argument for me – based on my past experience of students)

WRITE YOUR ARGUMENT HERE

______Premise=______

______

______Premise=______

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Conclusion/Theis=______

______

  1. Valid verses Truth

A VALID argument does NOT mean it is proven TRUE.

Ways to identify invalid argument:

  • if/then – be very skeptical, look carefully at the if. This might be valid, but only determined Strong or Weak, not necessarily true
  • some, most – particular terms. Invalid arguments speak only of particular groups.Also two particulars terms do not equal a universal.
  • all, none, every – Universal terms. Valid arguments have at least one universal premise.Universal conclusions must have two universal particulars.
  • Negative/ Affirmative – two negatives do not equal a positive. Two positives do not equal a negative. You must have at least one positive premise for a valid argument.
  • Common terms in both premises must appear in the conclusion.

Dogs can Fly.Valid Argument

Fido is a dog.False Premise

Fido can fly.=Valid but False

Some cats are blackNo Universals

Some black things are tables True Premises

Some cats are tables.=Invalid and False

Dogs love food. Invalid

Gilly loves food. Term “Food”

Gilly is a dog Truth unknown

People with Toyota 4 Runner own SUVsWrong Order

Joe does not own a Toyota 4 Runner Switch the last two

Joe does not own aSUV. to be Valid& True

  1. Argument, persuasion, or propaganda

Argument – based on objective (fact)

Persuasion – some objective (fact), some subjective (opinion)

Propaganda – all subjective (opinion)

To be determined as you write your outline

  1. Ethos, pathos, logos

Your language – what does it refer to?

Ethos – a credible source (Strong)

Pathos – emotional appeal (effective but does not strengthen validity.)

Logos – logic (Strongest)

You may use all three, but beware which you use most. To be determined when writing paper

______Premise=______

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______Premise=______

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Conclusion/Thesis=______