In ancient Greece, Socrates was reputed to hold knowledge in high esteem.
One day, an acquiantance met the great philosopher and said, Socrates, 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 triple filter test.'
'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. The first filter is truth - have you made sure that what you are about to tell me is based on fact?'
'No,' the man said.
'So you don't know if it true. Is what you are about to tell me about my friend is something good?' asked Socrates.
'Er no, actually..'
'So, you want to tell me something bad about this friend and are unsure as to whether or not it is true? Is what you are about to tell me about my friend useful?'
'Err, not really'
'So not only is what you are about to tell me untrue and bad, it is also of no importance? Why do you want to tell me?'
That, dear friend, is why there was no DM in ancient Greece..