What is the ‘hard problem’ of consciousness?

Consciousness seems like a very different kind of thing to the inert matter of the physical world. Yet we, who are conscious, are made out of such matter, complete with our brains and nervous systems. Furthermore, it seems that without our brains and nervous systems we would not be conscious. So, the puzzle arises, how do creatures like us, entirely made out of matter, become conscious? One influential answer comes from Descartes: consciousness is the essential feature of the mind, and mind is simply a completely different kind of thing from matter. We humans are a composite of both - the so-called ‘ghost in the machine’. This answer might well seem extraordinary to contemporary ears, especially to those of a scientific bent of mind. Many today tend to think that the world is made of matter alone, moving according to the laws of physics. We humans are the product of millions of years of evolution. So consciousness, whatever it is, must be something fundamentally physical, no doubt something to do with those incredibly complex brains and nervous systems that we have evolved. But hang on: intuitively, there seems to be more to it than this. Imagine for a moment the taste of chocolate, the texture of velvet to the touch, the chill of ice on your skin. It seems as though there is something it is like to have those experiences. In other words, they have a felt subjective quality to them, known only to the person having them. But if consciousness is essentially characterised by this felt subjective quality then it looks like there’s something substantial about consciousness that’s simply being left out by an explanation in terms of physical properties. This apparent gap in the explanation of consciousness - of how to understand the essentially subjective nature of consciousness in purely objective physical terms - has come to be known as the ‘hard problem’. What are its implications? Are we forced to agree with Descartes, that mind and matter are just fundamentally different and distinct kinds of things, consciousness belonging to the mind? Should we find ever more clever ways of trying to bridge the gap and make consciousness compatible with a physical world? Or will it remain, as some philosophers think, a problem shrouded in mystery that creatures like us simply cannot solve.