Here is Robert's advanced Advaita philosophy:
Robert pointing towards your goal at a blackboard: Becoming Nothing. Becoming Nothing is the last state you can have any involvement in method or goal.
However, there are Advaita Gurus with lots of concepts. If you read Ramana Maharshi literature you'll find lots of concepts because so many Indian philosophers went to Ramana and asked philosophical questions. But Ramana only himself had two methods: self inquiry via the question "Who am I?" and surrender to God and Guru. It is so, so simple, but so many make it so, so complicated.
Every Sunday Robert offered attendees a bouquet of concepts. Sometimes at the end of his talk, he'd say, "I just made that all up because some of you like concepts."
He taught self-inquiry as his primary method but taught many other methods too, because a lot of people couldn't locate any sense of 'I" even though they used phrases containing "I" hundreds of times every day.
Now, if you want concepts, below is a picture that explains everything in Advaita from the viewpoint of how Pradeep Apte sees Nisargadatta. If you read Maharaj, his talks are full of philosophical concepts. But they are all illusion. They do not help you except for a few moments when you feel like you finally understand Robert, Ramana, or Nisargadatta, and the mind feels a great relief and a sense of being at rest.------- At least for a few hours or days or weeks, when the doubts and questing begins again.
Here is the map that will explain everything and make it all clear. NOT!
Click this image once or twice, and it will expand 3 fold, making it readable.
Zen is called a transmission of the teachings outside of the scriptures. That is, it is truth not dependent on ideas or concepts. There is no truth in concepts or words, or ideas. Truth is when you grasp your existence before your mind is born. The mind can only reveal "understanding," which is temporary, and incomplete representation. You need to go beyond the mind, beyond experiences altogether. This also is what Robert taught when he said even consciousness lacked real existence.
When all concepts are dropped, when the glass becomes completely empty, stay there for awhile, and there you will find real freedom, far, far beyond understanding, along with complete happiness and peace.
Here is a link to Robert's Audio talk, "The good for nothing man." I think this was the second talk I ever transcribed and is still one of my favorites.
Really, don't take all this stuff too seriously or you will miss it altogether. It is not real. Your apparent life is not real. The world is not real, and all spiritual teachings are not real. This has to be your final understanding, but don't suffer too much in the process of seeking. It is far, far more simple than you think it is. Just drop thinking and merge into the I Am and then beyond I Am.
While it sounds simple, and is simple, persistence and focus are needed along with complete trust in yourself. That is, you make up your mind that nothing in life is worthwhile other than the freedom of liberation, and then dedicate your life to the one technique suggested by all real Advaita teachers, namely, self-inquiry. After practicing self-inquiry for a while and reading about all the different ways it can be done, focus on the instructions about self-inquiry found in the Path of Sri Ramana Maharshi, Part I, chapters 7 and 8. Then GO! From this point on, only go forward, not checking constantly as to momentary experiences or new understandings that arise. Just keeping sinking into the foreground and background, the I-sense and the witness of the void.