You're right that time is a property of the universe, which started up with the universe. But being a property of the universe it is therefore not nothing. But I used the word 'source' because the issue is not merely the "beginning" of the universe but the source of it. I am trying to emphasize that it couldn't pop into existence out of absolute nothing. Even if it has always existed with no actual beginning is beside the point because it has to have a source of origin even if it doesn't have a starting point in time. So, correct me if I'm wrong, but a quantum vacuum is not nothing, but a state of physical conditions with mathamatically describable properties.
Cordially,
You're right, but once you remove that from a historical sequence (i.e. time), it is equivalent to saying that there isn't just nothing. In other words, existence exists.
The concept of "causation" presupposes time.