No.
This guy is preaching a rubric that perpetuates itself on itself and does so in a fashion that saying "existence defines this, but the definition of this does not define existence" is not farce. It's the ultimate self perpetuating notion of cyclic ideologies and immediately we can fathom countless counter arguments to the basic argument set forth in this notion.
Creation is (by our understanding, his included) to encompass the notion that nothing can come into something. We do it on a daily basis, in fact. The ideas created by this guy are a testament to that notion. That he can dream up a dream from a place that did not exist prior to that dream. Drawing directly from that nothing into something.
Therefore, we can easily define non-existence within the parameters in which it exists by our definition.
Repeating something I've put in one of your prior threads... Time does exist without our consent. It functions without our conscious perpetuation seeking to iterate the cogs that provide it with functionality. It is and always will be. It is the alpha and omega of all things. We have only placed it within a protocol that it can function rationally within our own minds. Nothing more.
And to say we cannot imagine non-existence? Really?
Have you ever fallen asleep and woken up hours later with no recollection of anything during that time? The void we created during that time?
Yeah. Pretty indicative of being able to encapsulate the notion of nothing.