Many spiritual traditions speak of one non-dual experience. If there is no separate self witnessing experience, there is only experience. Generally they to not speak of a difference between inner and outer experience despite the fact our inner, subjective worlds are private to us, while the collective public world is "out there" and is measurable, with laws of science, motion, etc., all of which can be described and measured.
Strangely, many of these same unity-experience people will say we create our own public or outer world based on our internal beliefs and attitudes. Some even say the external world we live in is really a "projection" of our inner world. The outer world is a proection of who and what we are. Absolutely none of these people can speak to the question of who is projecting (conscious or unconscious), how is the projection accomplished (what are the mechanisms), and how real then is the external (public) world?
Certain Advaitins hold that there is no external world, there is only us, either as one unity experience, or us as witness, which creates a duality between witness and the witnessed, which could be either the internal/external world, or just the external world.
You see, there is such loose thinking here that everything stated in such generalities just does not make sense. If the external world is in any way connected to our internal world, what are the mechanisms? Does the term "projection" really mean anything? What is projected, the external physical world somehow comes out of our inner world? That chair in the corner of this room was created by me?
How on earth can I create an external world? How could I do this? How could all that vast external space and world come out of me, as when I look inside, I see/feel nothing like what is in the external world. If I am creating the external world, how am I doing it?
Science says there is an external world which we perceive through our senses and they speak to the complex mechanisms of light, sound, touch, odors, and tastiness are the way we perceive that world based on nerve impulses caused by external objects impinging on our eyes, ears, nose, etc. There is a whole science that explains how our bodies and minds perceive the external world.
Anyone who claims that the external world is created by us, especially created by our ideas and attitudes, need to posit explicit mechanisms so that this theory is helpful in any way, or can lead to predictions of any sort.
I have seen them present no theory other than we create the world we live in, and we can change our external world by changing ourselves--somehow.
Often they mean our attitude and mood can change what happens in our external world. That is, if we are positive thinkers, somehow our external world will better in some general way. Better how? Happier? More productive? More money and sex? More possessions? Bliss?
They do not go into detail nor present a theory about mechanisms. So whatever they say is just a useless, unprovable, pep-talk: think positive and you will be happy, productive, inherently lucky, and wealthy.
They would say there is no need to look within to fnd a self, because there is no separate self; even a cursory 3 minute investigation proves there is no inner self. They would say further that just looking for a self or seeking truth in the external or internal creates a tension that is inherently stressful and prevents happiness and rest.
So they say, "Do nothing; just be who and what you are." Of course this goes against 3,000 years of Western Philosophy that said, "The unexamined life is not worth living," and the Greeks who said, "Know thyself."
It also goes against the great Eastern traditions of Buddhism, where Vipassana, Mahayama, Theravadin, with complex methods of meditation, created dozens of generations of spiritual masters and monasteries. Ditto the Advaita of Shankara, the Hindu and Buddhist Tantric traditions, Confucian exploration of the moral, Christian and Muslim mysticism, etc. None said there was no need for intense spiritual effort. For most finding their truth of their own Self was the only thing that mattered and they spent most of their lives to find it, unlike the bevy of New Age twenty-something gurus who know only showbiz spirituality.
Krishnamurti, of course, rejected all those traditions, but recommended an even more difficult path, one where you needed to become extremely attentive, globally aware of everything, and disbelieved any theory taught to you. You were the single explorer and had to shed all that you have been taught. His was not just a sitting around and doing all that you did before.
But these new teachers are saying, "Be dumb; do not explore; do not look within; do not seek out gurus. I this way, you will be complete and happy." No wonder they have a large following; they speak of instant spirituality requiring no effort. It works for a while, but after a few months or years they see it was immature narcissism.