In ancient Greece, Socrates was a knowledgeable philosopher(哲学家). One day one person met him 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 a little test. It's called the Triple Filter Test(三重过滤测试). Before you talk to me about my friend, it might be a good idea to take a moment and filter what you're going to say. That's why I call it the Triple Filter Test. The first filter is truth. Have you made absolutely(完全地) sure that what you are about to tell me is true? ""No," the man said, "actually 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. Is what you are about to tell me about my friend something good?" "No, on the contrary…". "So, "Socrates continued, "you want to tell me something bad about him, but you're not certain it's true. You may still pass the test though, because there's one filter left: the filter of Usefulness(有益性). Is what you want to tell me about my friend going to 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 tell it to me?"