> They missed the point. There’s no such thing as silence. What they thought was silence, because they didn’t know how to listen, was full of accidental sounds.

The notion of "without stimulus" seems related to the use of "silence" in what Cage is saying here. Personally I would say that it's not that there's no such thing as silence, just that it's relative, and in this case "without stimulus" is relative to the audience's (reasonable) expectation at a concert hall.