An expression meaning that whatever "it" is- an idea, usually- it should be
obvious from
context that the point is true.
"It goes without saying that Google is the best search engine around."
However, I've always liked the following excerpt from one of my favorite books of all time, The Phantom Tollbooth:
Milo and Tock stood blinking in the bright light and, as their eyes became accustomed to it, the first things they saw were the king’s advisers again rushing towards them.
‘Ah, there you are.’
‘Where have you been?’
‘We’ve been looking all over for you.’
‘The Royal Banquet is about to begin.’
‘Come with us.’
They seemed very agitated and out of breath as Milo walked along with them.
‘But what about my car?’ he asked.
‘Don’t need it,’ replied the duke.
‘No use for it,’ said the minister.
‘Superfluous,’ advised the count.
‘Unnecessary,’ stated the earl.
‘Uncalled for,’ cried the under-secretary. ‘We’ll take our vehicle.’
‘Conveyance.’
‘Rig.’
‘Charabanc.’
‘Chariot.’
‘Buggy.’
‘Coach.’
‘Brougham.’
‘Shandrydan,’ they repeated quickly in order, and pointed to a small wooden wagon.
‘Oh dear, all those words again,’ thought Milo as he climbed into the wagon with Tock and the cabinet members.
‘How are you going to make it move? It doesn’t have a –‘
‘Be very quiet,’ advised the duke, ‘for it goes without saying.’