A famous teacher

Among the great teachers of ancient Athens was one named Protagoras,(who was born more than twenty-four centuries ago).It is said that he was the first teacher to accept money for his services.
A certain student,Evalthus,heard of this famous teacher and asked him to give him lessons.Evalthus did not want to pay for his lessons at ones,and after some discussions it was finally agreed between them that Evalthus should pay only if he won his first case in the law courts.
The lessons began and Evalthus proved himself to be a clever student.He worked hard,and a time came when he had reached the end of his studies.He then refused to pay Protagoras anything whatever.Protagoras therefore took Evalthus to court and told the judges that he wanted his money.He explained that he must be paid wether he won or lost the case."Whatever you decide,he declared to the judges,I must be paid.For if you decide in my favour,then I win the case,and so I must be paid.But if you decide against me,then Evalthus has won his first case in the law courts; therefore,according to our agreement,he must pay me for his lessons.Theefore,I shall get my money whatever happens".