In ancient Greece, Socrates was reputed to hold knowledge in high esteem.
One day an acquaintance met the great philosopher 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 Three Filter Test.”
“Three filter?”
“That’s right,” Socrates continued. “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 three filter test.
The first filter is TRUTH. Have you made absolutely 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 really know if 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. Is what you want to tell me 
about my friend going to be useful to me?”
“No, not really.”
“Well,” concluded Socrates, “if what you want to tell me is neither true nor 
good nor even useful, why tell it to me at all?”