It certainly is! The proof lies in the "fake hand" experiment, where the brain assimilates a fake hand as the real thing. Optical illusions are hallucinations where the brain makes a best guess of reality.
But does it matter? The brain produces "action potentials" that act on the muscle fibers and trigger a physical response. Not all intentional physical action is precise, but relies on a "best guess", and "best muscle control".
And it appears that the simplest organisms like single cells can also have the ability to communicate and relay data, making the cell a tiny data processor (unconscious brain) as well.
This can demonstrated with the quasi-intelligent behavior of the multi-nucleic single-celled "slimemold" that already displays a high level of "problem solving" survival skills.
This cytoplasmic blob is capable of astounding feats of "best guesses and logical behaviors". A slime mold can "walk" (pseudopodia), solve mazes, draw maps, tell time, react to temperature. And, in nature, we can see them do it.
Human body-cells also communicate from cell to cell, human brain driven ability to walk is still performed at the cellular level by the same cellular communication system as a slime-mold, but is triggered by an evolved brain that controls the production of action potentials.