One day a person met Socrates and said, “ Do you know what I just heard about your friend?”
"Hold on a minute ,” Socrates replied. “Before telling me anything I'd like you to  pass  the  Filter
(过滤) Test.” “Filter Test?” “Yes.” Socrates continued. “Before you talk to me about my friend, it
might be a good idea to filter what you're going to say. That's why I call it the Filter Test. The first filter
is Truth (事实). Have you made sure that what you are about to tell me is true?” “No, in fact I just
heard about it and...” “ All right,” said Socrates. “So you don't know whether it's true or not. Now let's
try the second filter, the filter of Goodness (好处). Is what you are about to tell me about my friend
something good?” “ No, quite the opposite...” “So," Socrates continued, “you want to tell me something
bad about him, but you're not certain if it's true. Now there's one filter left: the filter of Usefulness
(有用). Will what you want to tell me about my friend be useful to me?” “No, not really. ” “Well,” said
Socrates, “if what you want to tell me is neither true nor good nor even useful, why will you tell it to
me?”
       We can always join in loose talks(闲话). But when it comes to our friends, it's not worth it. Never
talk behindthe back about our near and dear friends.