A Lawyer named Protagoras teaches law for a hefty fee. He advertises his skills as a teacher by offering his students a contract, which states that they do not have to pay him until they have won their first case. If the student loses their first case, then they don't have to pay Protagoras at all.
One student of Protagoras sees a loophole, takes the course and fininshes it. After that, the student avoids arguing any cases.
Since the student has not yet won his first case, he avoids paying Protagoras.
Protagoras feels cheated, and sues the student for his fee. When the case comes to trial, the student represents himself. If the student loses the case, then by the terms of their original agreement, there is no fee for the course. If the student wins the case however, then, since its the student's first case, there will be a fee. (But, of course, winning the case means that the student doesn't have to pay the fee, while losing it means that the fee must be paid.)
Will the student be obliged to pay Protagoras' fee or not?
If the student loses, the court will order him to pay Protagoras. The student will immediately appeal, this time using a different lawyer to represent him, rather than representing himself. If he wins the appeal, he is home free -- clearly he does not have to pay. If he loses the appeal, he will appeal again, again using a different lawyer to represent him. He will keep this up until (a) he runs out of appeals, at which time he will pay Protagoras; (b) Protagoras dies of old age, which means the student won't have to pay; (c) he wins one of the appeals, upon which he won't have to pay.
If the student wins, the court will free him of his debt to Protagoras. Then Protagoras will immediately appeal, citing the legal ground of "changed circumstances" - the student has already won his first case, and so in this second case, Protagoras will argue, successfully, that the student must pay the debt. The student will pay Protagoras.
To sum up:
The student probably will NOT pay if he LOSES the original case (unless he exhausts the appeal process), but probably WILL pay if he wins the original case. This is a pleasing example of a paradox that the Ancient Greeks were so brilliant at creating.
Here is my ingenious solution
