LL.10 Guess what I'm thinking

Father said to his son.

"Here is 1000 yen. If you can estimate what I consider, I will give you this 1000 yen." 


Is there any answer by which he can get 1000 yen ? 






Answer
Yes, there is.

Solution
The answer is 
"You think that you believe that you do not give 1000 yen to me".

If the father thinks just like that, then the son can get 1000 yen of course.

If the father thinks another thing, since a father thinks "he does not need to give 1000 yen", when he thinks so, it will become a correct answer.

It is forced by the father is forced to give 1000 yen after all.