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?