Cartesian dualism has been a point of contention in philosophy since at least, well, Descartes. The dispute is whether the mind is a separate, immaterial entity from the physical body. Problems have plagued the dualist view since the time of Descartes, primarily how it is that the immaterial mind and material body interact.
Consciousness and qualia are problems that are still unsolved by philosophy, psychology, and neuroscience. My way of viewing consciousness and qualia is that consciousness is the process by which our brains organize the world into working models and qualia is the ‘stuff’ that consciousness uses to generate those models. For better or worse, both of these exist due to evolutionary forces. That means they’re fine tuned to a very specific sort of survival, not for any pure understanding of the world or ourselves. In order to understand the limitations of our own minds, we need to know the inner workings of how the world is organized in our minds on a fundamental level. That requires knowing the structure of our minds.
The first law of thermodynamics tells us that energy cannot be created or destroyed, only converted into other forms of energy – for example, if you slap the wall, the mechanical energy that goes into the slap is converted into the energy needed to produce sound. With Einstein’s famous equation E=mc^2 it is easy to see that conservation of energy translates into conservation of matter.
This dictum applies to the physical reality that we inhabit. But what about the individual that experiences this physical reality? What is the mind?