It's so memorable, probably why it stick in my memory: how can you have a canvas without a wall? The wall is the canvas. Yet the wall simultaneously constrains the canvas, thus allowing it to become the canvas, to become worthy of a canvas. This French idiom says so much without saying practically anything.
>>public+(OP)
Coming back at this with a fresh mind, whoever said it could also have meant that every painting should be displayed: it requires a wall to hang on.
As you say, it's not immediately clear what is meant.
>>dxdm+rf1
Even more evidence of how versatile that French phrase is. There's just so many acceptable meanings to it, and every one of them points to the same conclusion: bounds enable art.