Let's take a break from moral philosophy for a moment.
Consciousness (i.e., all mental states) is just states of the brain, functional states, like software being run, but nevertheless physical like software, rather than non-physical. The program running your web browser right now is physical, and, by the same token, so is the consciousness in your brain. Here's why.
If consciousness were non-physical, we could conceive of a physical, human body operating normally, exhibiting the behavioral and brain states of a normal person but being devoid of any consciousness. "Hello," it might say, as it smiled and shook your hand, with the lights on but nobody home. In other words, if consciousness were non-physical, it could be peeled away from the brain in a thought experiment such as this. We could conceive of the brain working its neural net as usual but without any consciousness being generated by its activities. Such a being we could call a "zombie," but it wouldn't be like the zombies in the movies who act sleepy. Ex hypothesi it would act just like you and I.
This is all boilerplate in contemporary philosophy of mind. The problem is the whole field zigs where it should zag. It accepts that zombies are conceivable and then either tries to squirm out of the resultant dualism somehow or just gives up and accepts dualism. But we cannot conceive of zombies. To conceive of a kind of thing requires that one have an idea of what would count as evidence that there was a thing of that kind. To understand "apple" requires knowing what counts as evidence that there is an apple on the table, for example. But no one has any idea what would count as evidence that someone was a zombie. Look into its eyes, shake the hand, but, try as you might, you have in principle no way of telling that your new acquaintance is a zombie. Does he not cry when hurt? Does he not swoon during courtship? Ex hyposthesi he does. So, the concept of "zombie" is meaningless. The word "zombie" is as meaningless as "round square". Therefore, "consciousness is non-physical" is incoherent.
This proves that consciousness is nothing more than synapses firing. It is inconceivable that mind and body exist separately.