Socrates was famous in ancient Greece for his knowledge. One day, one of his friends went up to him and said, "I've just heard something about your friend, do you want to know?"
"Well," Socrates said, "Before telling me anything, I'd like you to pass a test. It's called the triple filter (三重筛选) test."
"Triple filter?"
"That's right," Socrates continued, "Before you talk to me about my friend, it is a good idea to think about what you will say. The first filter is ________. Are you sure what you are going to tell me is true?"
"In fact, I just heard about it and…" the man said.
"All right," Socrates said, "So you don't really know whether it's true or not. Now let's try the second filter—goodness. Is what you are going to tell me good?"
"No, on the contrary (相反)…" the man replied.
"Okay," Socrates continued, "The last filter is usefulness. Is what you are going to tell me useful to me?"
"No, not really." The man said.
"Well," Socrates ended, "If what you want to tell me is not true, good or even useful, why tell it to me at all?"
