Mind-body dualism is the belief that the brain and the mind are separate. This disembodied mind is sometimes referred to as the soul or the spirit. Supposedly it attaches itself to the living human being and continues to live and exist after the human being dies. The most important reason why nobody should believe this is that there simply is no evidential basis for it. In this essay, I will argue that not only is there no evidence for the disembodied mind, but there is plenty of evidence against it.
The undeniable fact is that when something happens to the brain, that very same thing happens to the mind. If the brain malfunctions, the mind malfunctions, if the brain is damaged, the mind is damaged, when the brain is inactive, so is the mind.
When we sleep, so do our minds. We may have dreams that make sense sometimes, but much of the time they are nonsensical. People morph into other people, scenes suddenly change, physics is all over the place. If the mind is the rational conscious bit that we need to function and it is not present in dreams, where does it go while we dream and sleep? Most dreams indicate that the mind takes a break when the brain takes a break. When we are unconscious our brainstates change, and these states can be measured. Just as you would expect with a strictly physical mind. If we have some sort of rich mental life outside our bodies at night when our brains are sleeping, why does it disappear the next day? This makes no sense.
When we suffer brain damage, we can forget things. We can lose some aspects of our personality or gain others. Aspects of our personalities can change drastically. For instance there is a man who can never be sad and the infamous case of Phineas Gage shows that personality is intimately linked with the brain. So there is ample evidence to show that the mind is an endogenous effect of the brain when we look at damage, because we consider our personalities part of our minds, and damaging the brain damages the personality.
Emotions have been mapped to physical processes. We know that love is a combination of hormonal effects in the brain. The favourite topic of research nowadays is a neuro-transmitter called oxytocin that has shown to facilitate kinship bonding. Whenever we feel emotions there are certain physical causes of those sensations that result in what we normally characterize as signs of those emotions. Our love, hate, sadness and happiness are all just self administered chemical injections. In fact we do much of what we do to chase experiences of happiness and love, making us drug addicts on the very fundamental level of our physiology. The assumption that there are some emotions that transcend the mind doesn't make sense. There is no reason to posit such a thing either because we can see emotions acting physiologically in our brains.
A large part of what we consider our identities are based on our memories too. Does someone with severe dementia have a perfectly functional soul behind their fading identity? In a very real sense neural degeneration is slow death. The identity of that person slowly degrades into nothingness. It's tragic but illuminating. Where does the mind go during this traumatic time? Does it leave the body early and continue into the afterlife, leaving an empty husk? Does it just sit there, unable to communicate with the outside world because the brain is broken? What would a supernatural thing have to do with physical processes anyway? Why could a physical process impair its function? That makes absolutely no sense.
If our emotions, our memories, our conscious waking hours and our personalities are all intricately linked to physical processes in the brain, then what possible justification is there besides wishful thinking to posit such an imaginary piece of disembodied magic? Does our lack of a complete map of every brain function warrant a belief that the mind cannot be caused by the brain? Nope. Does the problem of describing consciousness fully mean that we need to posit imaginary entities to pretend to knowledge we don't have? Certainly not.
You, me and everyone else are just our brains. Whatever happens to our brains happens to us. There is no reason to imagine a disembodied mind to explain the perplexing facts of neuroscience and psychology because it would be totally superfluous.