The Philosopher Café Meeting

September 14, 2005

 

I.                  Book/Media Discussion – 6:00 – 6:10

o       The Philosopher’s Toolkit, Mel Thomas

An excellent introduction to logic and common fallacies.

 

II.               The Challenge:     6:10 – 6:30 PM

 

III.            Introduction – Theme is Logic  6:30 – 7:00 PM

 

Definition: Key distinction between western and eastern philosophy is that western philosophy is founded on logic though there have been some deviations from this.  Logic is the rules by which we come to accept something as true. It’s critical to evaluating competing claims.

 

Defining what you mean and Destroying an Argument

 

• The Socratic Method
• Defining Terms

 

Induction vs. Deduction

 

Induction -  Making a claim based on observations of a subset of a class, example, 1,000 crows are black so you conclude all crows are black. “Universal Proposition”

 

Generalizations based on induction cannot yield strict certainty.

 

Deduction

 

The Structure of an Argument

• Claims, aka Premises and Conclusions

                       If you pass the test, you will pass the course - Premise

You passed the test – Premise

Therefore you will pass the course. - Conclusion

 

• True or False
  • Strict Certainty vs. Practical Certainty

 

Practical certainty = very, very likely but not 100% definitely true. Example, “I am standing in front of a group a people right now.”

The “What if I am dreaming?” test.

 

Strict certainty = No doubt that it is true.  Example, the corners of a triangle add up to 180 degrees.

Even if I am dreaming.

 

It is very hard to get strict certainty for most things in life. Descartes was going for this.

 

• Justified vs. Unjustified Certainty and a Pile of Turtles
• Argument Forms

 

Syllogism

           All men are mortal.

Socrates is a man.

Therefore, Socrates is mortal

 

Modus Ponens

 

If it rains, my will get wet.

It did rain.

My car got wet.

 

If p, then q.

p.

Therefore, not p.

 

If it rains, my will get wet.

My car is not wet.

Therefore, it My car got wet.

 

 

If p, then q.

Not q.

Therefore, not p.

 

Soundness and Validity

 

           Valid = If the premises are true, the conclusion must be true.

 

                       Sound = Valid and the premises are true. 

 

Common Fallacies

 

Premise 1: If the garbage men have been here, then my garbage cans are lying empty next to my shed with their lids off.

Premise 2: My garbage cans are lying empty next to my shed with their lids off.

Conclusion: Therefore, the garbage men have been here.

Next, we determine the form of the argument. It is,

If p, then q

q.

Therefore, p.

 

If my house is being foreclosed on, I will get a letter from the bank.

I got a letter from the bank.

Therefore, my house is being foreclosed on.

 

 

Affirming the Consequent

When invited to explain his argument, he began by telling us "The Koran says in several places that we do have a duty to take care of those who are less fortunate than we ourselves." Some of his listeners responded, "So? Where's the proof you promised?" "I'm only working on the first premise," he gave back. "It is, 'If the Koran is the word of God, then we do have a duty to take care of the less fortunate.'" "That's still not an argument," someone observed. "Just wait," my Moslem friend continued, and, "Don't you agree that we do have a duty to take care of the less fortunate?" "Of course," someone in the audience said. "Well," the Moslem stated, "That takes care of the argument. Just put two and two together, and you'll have a proof that the Koran is the word of God, a proof just as solid as Fritz Wenisch's garbage can example."

Here is that argument:

Premise 1: If the Koran is the word of God, then we do have a duty to take care of the less fortunate.

Premise 2: We do have a duty to take care of the less fortunate.

Conclusion: Therefore, the Koran is the word of God.

If Bill is on a diet, Bill will order sherbet.

Bill is not on a diet.

Therefore, Bill will not order sherbet.

Denying the antecedent.

IV.             Open Discussion Question 7:00 – 7:30

  

Self Defeating Claims

 

• “You cannot know anything for certain.”
• “You cannot understand communication from outside a culture/society.”

 

Logical Absolutes, For example “Omnipotence”

• God is omnipotent
• Therefore, God can do anything.
• God can create another omnipotent God.
• God can destroy Himself.
• Therefore, atheism, monotheism or polytheism could all be true.

 

Also, omnipotence and omnibenovolence leads the problem of evil know as “theodicy”.

 

“Everything I say is a lie.”

 

“This statement is false.”