A question about oneness of Allah

One of our readers has asked the question below, It will soon be replied. 
Thanks fro your patience

A good way to learn about Islam. 
Thank you for "have your say" part. 

One of my friends who reads RN wanted me to ask you that question. He said the answer is in Risale-i Nur. Hope you can send a suitable answer. 

"Muslims always say, there is only one god. I am a muslim too, and I believe in God.

As far as I learnt, proving the existence is easy (as written in RN). For example an apple in a city. If you show it, it's proven. Ain't no problem. 

How about the nonexistence???

Guess there are two gods. 

One god wished to create the world. Ok, I believe the one is the creator. 
One letter can't be without a writer and one needle can't exist without a doer. that's right. 

But why can't exist a Second god Having Full Power and Attributes of the first god but NOT Wishing to create anything.

According to the rule in RN, in order to prove some being's NON-Existence you have to search all the universe. Perhaps there is a second god but he doesn't create anything but exists.

You may reply saying;
Every good being wants to see and show his goodness. So if there were a second one, he would wish to create. 

I say, 
if he's GOD, he is not obliged to show it. and he is not Obliged to do anything. 
If he is a god, there is no obligation for him. Can anyone prove that there is not a second GOD who does not wish to create?"

Do it for my friend.

Thank you for your time.