Friday, July 21, 2017

July 21, 2017 Friday

Bedtime Story 


Abhari and the Negation of Conjunction


Abhari took the following sentence into consideration while analyzing the Liar Paradox:

“All that I say at this moment is false.”

Before giving the solution, or what he considered a solution, he gave the following analysis of the paradox.

“This statement is either true or false.

If it is indeed true, then it must be both true and false.

And if it is not true, then it is necessary that one of his sentences at this moment is true, as long as he utters something.

But he says nothing at this moment other than this sentence.

Thus this sentence is necessarily both true and false.”

Abhari offered the following solution to the Liar paradox:

“To solve the paradox we should not concede that if it is false then one of his sentences is true.

For its being true is taken to be the conjugation of its being true and being false.

Therefore its being false necessitates the non conjunction of its being true and being false.

And the non-conjunction of its being true and being false does not necessitate its being true.”

I know it does not make much sense.

Abhari is invoking here some of the fundamental laws of logic that in modern days go under the name of negation of conjunction and negation of disjunction.

Anybody who has done a basic course on Boolean Algebra or propositional logic would know of De Morgan’s laws.

Let me state these laws before we discuss them.

Negation of conjunction is the disjunction of the negations.

Another way of stating it in the terms of set theory is that the complement of the union of two sets is the same as the intersection of their complements.

In more formal language, the negation of conjunction would appear like this:

¬(P ⋀ Q) ⇔   (¬P) ⋁ (¬Q)

where P and Q are two propositions.

⟺ is a metalogical symbol that stands for “can be replaced in a logical proof with”.

The other symbols are all too familiar to the readers of bedtime stories.

I will deal with the negation of disjunctions in the nights to come.

You might think all this too theoretical.

The fact is that these simple logical rules form the basis of the devises that you are holding in your hands.

Stay tuned to the voice of an average story storytelling chimpanzee or login at http://panarrans.blogspot.in/
                              
Good night mon ami and my fellow cousin ape.
                           
  
                

             












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Another great educator and a teacher that I am aware of is Professor Subhashish Chattopadhyay in Bangalore, India.

While I narrate stories, Professor Subhashish an electronic engineer and a former professor at BARC, does and teaches real mathematics and physics.

He started the participation of Indian students at the International Physics Olympiad.

Do visit him here:


All his books can be downloaded for free through this link:


For edutainment and English education of your children, I recommend this large collection of Halloween Songs for Kids:

https://www.youtube.com/channel/UCd14DRdYKj454znayUIfcAg

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