There's something strange about people who say "All is One" while believing in an immaterial soul or some other supernatural entity. This is a dualiistic idea that's at odds with oneness.
Materialists actually are the true monists, because they hold that everything in existence is formed of the same substance.
Michael Shermer makes this point nicely in his book, "The Believing Brain."
This process of explaining the mind through the neural activity of the brain makes me a monist. Monists believe that there is just one substance in our head -- brain. Dualists, by contrast, believe that there are two substances -- brain and mind.
This is a very old problem in philosophy dating back to the seventeenth century when the French philosopher Rene Descartes put it on the intellectual landscape, with soul the preferred term of the time (as in "body and soul" instead of "brain and mind").
Broadly speaking, monists assert that body and soul are the same, and that the death of the body -- particularly the disintegraton of DNA and neurons that store the informational patterns of our bodies, our memories, and our personalities -- spells the end of the soul.
Dualists contend that body and soul are separate entities, and that the soul continues beyond the existence of the body. Monism is counterintuitive. Dualism is intuitive. It just seems like there is something else inside of us, and our thoughts really do feel like they are floating around up there in our skulls separate from whatever it is our brains are doing.
We are natural-born dualists, argued Yale University psychologist in his book, Descartes' Baby. Children and adults alike, for example, speak of "my body" as if "my" and "body" are two different entities.
...The reason dualism is intuitive and monism counterintuitive is that the brain does not perceive the process of binding all the neural networks into one whole self, and so imputes mental activity as a separate source.
Hallucinations of pretenatural beings such as ghosts, gods, angels, and aliens are perceived as real entities; out-of-body and near-death experiences are processed as external events; and the pattern of information that is our memories, personality, and self is sensed as a soul.