One day, the old, wise Socrates walked down the street when all of a sudden an agitated man run up to him yelling: "Socrates, Socrates! I have to tell you something about your friend! You will not believe what I just heard!"
"Hold it right there," Socrates interrupted him. "The story you're about to tell me... did you let it go through the three sieves?"
"Three sieves?" asked the astonished man. "What three sieves, Socrates?"
"Three sieves, my good man. Three sieves. Let's try it," said Socrates.
"The first sieve is the one of truth. Did you examine whether what you were about to tell me was true?" asked the philosopher.
"Well, no, not really. I just overheard the story and was in a hurry to tell you..." said the man.
"Ah! Well, then you must have used the second sieve, the sieve of good?" asked Socrates. "Is it something good that you are about to tell me?"
"Hm, no... on the contrary, my dear Socrates," answered the man.
"Hmmm" the wise man said. "Let us use the third sieve then, the sieve of necessity. Is it absolutely necessary for you to tell me what you are so exited about?"
"Now that I think of it... No, it's not necessary at all," said the man.
"Well," Socrates said with a smile "If the story you are about to tell me isn't true, good, or necessary, just forget it and don't bother me with it anymore."
Sources of the story and the image unknown but greatly appreciated