Logical arguments, Part I
- 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=______
______
- 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
- 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
- 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=______