### Story

*
A family of Dad, Mom, and two children: a boy and a girl
*

**Mom**: Please go outside and observe the sky.

*The two children run outside, spend some time, and come back inside*

**Girl**: Mom, the sky is blue.

**Boy**: Mom, the sky is not blue.

**Girl**: It is blue.

**Boy:** It is not blue.

**Dad**: Okay, let's say we do not want to get in trouble.

Let's say we want to be safe and say the truth.

**Girl**: Then, believe me Dad. Go ahead and take a look. It is blue.

**Mom**: Alright my princess, we want to accommodate what your brother said.

We want to accommodate what you said and what your brother said.

And still say the truth to be on the safe side...

Can you make a true statement in that regard?

**Girl**: I do not understand, Mom.

Please explain.

**Dad**: How do you join the two simple statements - the one you said, and the one your
brother said; into one true compound statement?

You have learned connectives in English Language. Right?

**Girl**: Yes, Dad.

The compound statement would be: "The sky is blue OR the sky is not blue".

That way, it is either the sky is blue or the sky is not blue.

That is a true statement.

**Mom**: Correct!

In Mathematical Logic, we call that statement a __tautology__.

**Girl**: What is a tautology?

**Dad**: Tautology is a statement that is always true.

What is the "OR" known as?

**Boy**: It is disjunction.

**Dad**: That is correct.

**Boy**: What is Mathematical Logic?

**Mom**: It is one of the topics covered in Discrete Mathematics.

**Girl**: What is Discrete Mathematics?

**Dad**: It is one of the branches of Mathematics.

Can you form a statement that makes the two statements a false compound statement?

**Boy**: "The sky is blue AND the sky is not blue".

The "AND" is conjunction.

**Mom and Dad**: Correct!

In Mathematical Logic, we call that statement a __contradiction__.

**Girl**: It seems Mathematical Logic has a connection with what we are learning in English Language.

**Dad and Mom**: Yes, it does!

Interdisciplinary connection - Mathematics and English!

**Girl**: So, I guess ... a contradiction is a statement that is always false.

**Dad**: You are right!

**Girl**: But, how can that even be?

It does not make sense for the sky to be blue and also not to be blue.

**Dad**: That is the reason why it is called a contradiction... it is a statement that is never
true

It looks like the statement from that politician! - contradicting himself as usual

When a lot of people say the sky is blue, that politician will say the sky is blue.

When those same people turn around and say the sky is not blue, the politician will also say the
sky is not blue.

When some of those people say the sky is blue, and the rest of them say the sky is not blue; the
politician will say well: "the sky is blue and the sky is not blue".

**Girl**: Dad, I think I know the politician you are talking about.

**Dad**: Whatever...

*
The entire family mention the politician's name and laugh...
*