The brain is a central processing unity (CPU) and is one of many processors in the body. Or you could think of it as a sub-set of the software which performs a particular task.
The brain and all other processors do not do anything other than execute commands. The brain does not create commands.
The body executes all commands exactly and correctly. It does not invent commands itself, has no will of its own, and does not think.
The mind is not a by-product of the brain. That would be as though to say that the CPU of the body computer comes up with it own software programs, or that the software has the power to change itself.
The software programs MUST come from outside of the computer itself., from an actual source of WILL, capable of writing programs in the first place. And that intelligence must be able to function WITHOUT a body and without a brain!
That intelligence must be able to think without needing a body in order to think. It must be creative.
That mind, that intelligence, must also have designed the body computer itself, the CPU (brain) and all other parts. It must have devised all of the software that operates it.
Therefore the body computer is INSIDE of the mind, just as the programs which run on a computer come from OUTSIDE of the computer, created by an operator who tells the computer what to do.
Just because software runs inside the computer does not mean the computer is the source of the software. Similarly just because it SEEMS as though the mind operates inside the body, that the mind is created by the body.
The mind - the programmer - WROTE the body software, WROTE the brain, and WROTE all of the programs which the body/brain executes.
This is why looking for mind or thought within the brain, as though the brain is a "cause", or that the brain has a "will", or that the body has a "mind of its own", is completely a mistake.
The body does not have a mind of its own. It is just a functional machine, a device. YOU as mind put instructions into the device to tell it what to do. And it does that, and only that, exactly and correctly.
No matter what you tell the body computer to do, it will do it. If you tell it to depict health, it will. If you tell it to depict sickness and death, it will. It always produces a correct result because it does not pick and choose what instructions to follow.
YOU are therefore in COMMAND of the body, the world, and all illusions. YOU are the one who is writing the scripts (programs). YOU are the author.
Except that, it goes even further than this. God is really the only author of reality and truth. He is the only author of bug-free programs. He is the only one who can create the perfect program (Christ) which can in turn extend God's design to produce further perfect programs (Christ's creations).
But when you tried to become a SEPARATE PROGRAMMER, you tried to override God's program, shut it out, and replace it with a program of your own. Thus your ego wants to be fully in charge of the dream, to have power of it, and to even perform miracles, PROVIDED it gets to stay separate from God.
Fortunately miracles require sharing with God, so the ego will never be able to access God's power. Therefor the ego will never be able to rewrite the true program of Christ, and will never be able to actually corrupt anything.
Just as all bugs and errors and viruses and rogue programs are WIPED UNCONDITIONALLY from memory when you reboot your computer, when you awaken to enlightenment, God will REBOOT YOU, and after the reboot, all that will be left is the perfect program of Christ. A totally new, fresh system, untainted and undefiled. And you will express love and love will be your only output.