It took me several years of exploration to understand this passage from A Course in Miracles:
“You also believe the body’s brain can think. If you but understood the nature of thought, you could but laugh at this insane idea. It is as if you thought you held the match that lights the sun and gives it all its warmth; or that you held the world within your hand, securely bound until you let it go. Yet this is no more foolish than to believe the body’s eyes can see; the brain can think”.
The brain is unaware, and as such cannot understand thought. The brain is the instrument through which Consciousness can observe itself thinking. And the thoughts are themselves generated by the brain, but made of Consciousness.
Let’s look to experience - for example, hearing a sound. Our experience of the ear is one sensation that we are aware of. The experience of sound is another perception that we are aware of. If a hand blocks out the ear, the sensation around the ear becomes larger, and the sound disappears from experience. But both the ear and the sound are known by Awareness, the only dimensionless ‘thing’ that is aware. Being itself an object of experience, the ear does not know other objects of experience.
The same is true for sight - the body’s eyes are a tool through which Consciousness observes itself taking a particular form. The eyes do not know what is seen, it is Consciousness that knows.
Finally, the same is true for all other senses, and also for the brain. The brain allows Consciousness to experience itself in the form of thought.
Saying that the brain can think and the eyes can see promotes the idea that Consciousness is a product of the body, which leads to greed, violence, terrorism, etc. - please see my video 'the hard problem of Consciousness and its tragic consequences'.