It has been said that the parable of the three sieves by Socrates is but a myth, but be that it may, it is still worth repeating: 

One day, when Socrates had just left the place where he used to interact with young people about their way of conceiving life, he met a man he knew who told him, in a confidential tone:

Listen, Socrates, there is among your listeners a disreputable young man, unworthy of your trust. When I tell you what he’s doing, I think you’ll ban him from your group.

I am ready to listen to you, replied Socrates, and to take the necessary measures. But let me first look closely at what you are about to tell me. Have you passed your words through the three sieves?

The three sieves, questioned the man, what is it?

The first is the sieve of Truth. Are you sure that what you are going to tell me is true? Have you heard it yourself or watched with your own eyes?

To tell the truth, said the man, after a moment of hesitation, I just overheard it.

The test of the first sieve is not successful, says Socrates. Let’s examine the second: the sieve of Goodness. Will you tell me something good or positive about this man?

On the contrary, said the other, I was going to say bad things about him.

Your words do not pass the second sieve, says Socrates. Let’s use the last sieve. Is it necessary to tell me what you’re so excited about?

No not necessary, the man says.

Well, Socrates says with a smile, if the story you’re about to tell me isn’t true, good or necessary, just forget it and don’t bother me with it.