In a previous post ("I Hate My Brain") I argued for the separateness of the mind from the brain by appealing to myself and my awareness that my brain is suffering from Parkinson's disease. I noted that I (my mind) used to be driving along in a very nice car (my brain), but that the car now had flat tires and sand in the gasoline. While my mind can still tell my body to turn over in bed or stand up from a chair, my muscles just aren't getting the message, because the needed brain cells (the ones that make and receive neurotransmitting chemicals) are dying off, thus making it increasingly difficult to move around. Adding the missing dopamine helps a lot. My mind knows this.
In fact, my mind knows that am taking replacement chemicals (carbidopa-levodopa, rasagiline, etc.), but my brain doesn't know it.
This argument for mind-brain separateness is known as the introspection argument. Our minds can look at, respond to, and even judge our brains. Here are some examples.
1. I am aware that I'm not as sharp as I was when I was younger and in school. I know my brain has lost some of its acuity.
2. Sometimes I can't find the right word. My mind knows the word and knows that it's in my brain somewhere, but I can't remember it right now. Later, my brain might put the word into my consciousness. (I once couldn't remember a friend's name. Now that is disturbing. But her name came back to me in a few minutes.) As a curious footnote, I have noticed that when I'm searching my brain for a word, the candidate words my brain suggests are often nearby alphabetically. That is, it appears to me that my brain stores words in alphabetical order.
3. Sometimes I forget what I was going to say. When people are talking, I sometimes get a good idea, but before I can interrupt, I forget it. But my mind knows my brain is not performing the way I want it to and that I had the idea. If only I could remember it.
4. We can judge our brain's situation: our minds evaluate our brains. "My brain is not up to speed," we say when we feel groggy. Or, "There is something wrong with my brain today. I can't think."
5. Sometimes a person who has had an arm or leg amputated will feel pain in that missing limb. In such cases, the person's mind knows that the limb is missing and that the pain is coming from a false signal in the brain. "Stupid brain," they might say.
Our brains can malfunction in many ways, and our minds often know that. We can monitor our brains and judge when they are not working right, with the exception of severe malfunction, such as schizophrenia, where the brain is so broken that the person's mind can no longer distinguish between imagination and reality. My brother was severely schizophrenic, and since I once read that a sibling of a schizophrenic person has a 14% chance of becoming ill also, for many years I set my mind to watch my brain for any symptoms of hallucinations or delusions. And that is another example of the dichotomy.