Everything is a mental concept.
Anything that you can think about, anything that you can come up with your mind is a mental concept.
Whether it's God, whether it's the Self or whatever you're thinking about.
Therefore to get to these places you have to stop thinking totally and completely.
Use whatever method to stop the thoughts.
Whatever method that you have.
A method that you're used to.
Use whatever method that you like to stop the thoughts.
By ignoring them, by watching them, by asking,
"To whom do they come?
Who thinks?"
But by all means do something to keep the thoughts from attacking you, from telling you what to do and how to live.