Claim: The best test of an argument is its ability to convince someone with an opposing viewpoint.Reason: Only by being forced to defend an idea against the doubts and contrasting views of others does one really discover the value of that idea.

The author claims that the touchstone to assess an argument is its ability to convince someone with the opposing viewpoints. The author further reasons that this is the best way to prove an argument as it is only with the defending of an idea that a defender recognizes the value of that idea.

To begin with, if an argument tolerate the crucible of opposition indeed it is the best test of an argument. In definition, the nature of argument and the mores of argumentation, is to convince others whose views are opposite. In other terms, arguments to exist always need the arguers from two contrasted positions. Therefore, it is a self-evident fact that argument needs to convince the other as right or true to prove its validity. However, there are some circumstances that such an approach for evaluating an idea does not hold true.

When discussing the ideas do not follow a logical order, there would not be any convinced party at the end of the argument. There is an apt proverb here saying: You can awake the one who is asleep, but you cannot awake those who are pretending to be asleep. In many cases, the profits and advantages of one side party are at stake that even with knowing that it is not right, they strive not to be convinced. Furthermore, if a person is dogmatic also the debater may not be able to convince the dogmatic person as there is no logical common ground to reach a same point.

Finally, as far as the reason is concerned, the author perpetrates a fallacy of reductionism; defending an idea may be an effective way but it is not the only way to recognize the value of an idea. With defending an idea we are prompted to analyze all the weak points of our idea and this makes the idea have more realistic features. But the real value of an idea can be quite self-evident that there would be no need of any arguing. Consider myriads of the inventors and discoverers. The idea of making a lamp for example. The idea was so fascinating and valuable that Edison tried it a thousand times as he knew the value of a success even if it happens once in a thousand experiments of lamps.

In short, when any argument takes place on common grounds of logic, the convincing of the other party shows the advantage of the idea and its validity. However, when someone holds an idea, he or she does not necessarily need to convince others that the idea holds true, for some ideas are axiomatically valid.