Few centuries ago, a Law teacher came across a student who was willing to learn but was unable to pay the fee. The student struck a deal saying ' I would pay your fee the day I win my first case in the court'.
Teacher agreed and proceeded with the law course.
When the course was finished and teacher started pestering the student to pay up the fee, student reminded the deal and pushed days. Fed up with this, the teacher decided to sue the student in the court of law and both of them decided to argue for themselves.
The teacher put forward his argument saying : "If I win this case, as per the court of law, student has to pay me.
And if I lose the case, student will still pay me because he would have won his first case. So either way I will have to get the money".
Equally brilliant student argued back saying : "If I win the case, as per the court of law, I don't have to pay anything to the teacher. And if I lose the case, I don't have to pay him because I haven't won my first case yet. So either way, I am not going to pay the teacher anything".