Only by being forced to defend an idea against thedoubts and contrasting views of others does one reallydiscover the value of that idea."

The statment is actually twofold. The author
emphasizes that (1) the best way to appreciate an idea
is to be forced to defend it and (2) defending an idea
is the only way to trully discover its value. I agree
with the first statement insofar that the familiary
with the idea is somewhat obscure. The second
statement leads the reader to conclude that the only
way to really discover the value of an idea is to
actually defend it. Although I agree that backing-up
is very important, I don't whatsoever dismiss any
other type of building confidence on a subject, such
as by expertise, reading, or writing.

When someone is usually challenged on their point of
views or positions about issues, one is forced to
defend its thoughts by providing meaningful and
persuasive explanations. The defendant must therefore
concise all its knowledge about the matter and depict
it in a convincing manner, as well as being able to
refute other's thoughts. Admittedly, being forced to
advocate it...