Think before you speak.

In ancient Greece (469-399 BC) Socrates was widely lauded for his wisdom.
One day the great philosopher came upon an acquaintance who ran up to him excitedly and said: “Socrates, do you know what I just heard about one of your students?”
“Wait a moment,” Socrates replied, "Before you tell me I’d like you to pass a little test, it’s called the test of three.” “Three?” “That’s right,” Socrates continued, “Before you talk to me about my student let’s take a moment to test what you’re going to say. The first test is TRUTH. Have you made absolutely sure that what you are about to tell me is true?” “No,” said the man, “actually, I just heard it.”
“All right,” said Socrates, “so you don’t really know if it’s true or not. Now let’s try the second test, the test of GOODNESS. Is what you are about to tell me something good?” “No, on the contrary…”
“So,” Socrates continued, “you want to tell me something bad about him even though you’re not certain it’s true?”
The man shrugged, a little embarrassed. Socrates continued. “You may still pass through, because there is a third test – the filter of USEFULNESS. Is what you are about to tell me useful to me?” “No, not really.”
“Well,” concluded Socrates, “If what you want to tell me is neither True nor Good nor even Useful, then why do you want to tell me?” The man was defeated and ashamed.

This is the reason why Socrates was a great philosopher and held in such high esteem.

It also explains why he never found out that Plato was having an affair with his wife.