aranthur never did find out what would be different tomorrow , or after-tomorrow , or in his grandchildrens ' lifetime , as a result of that window being left open , but when he thought about it later , he realised that was why the worlds had to be infinite ; there would be one world in which he shut the window , one world in which ramutha had already shut it , or would shut it , and another in which the window stayed open , and perhaps a sparrow flew into the room ... has he been attentive ?