Imagine the smile on your parent's face as you rush to meet them at the school gates, the soft heat of the sand between your toes on a first holiday, waking up in the haze of a late afternoon after dancing all night, the drop in your stomach when you realize you'll never hear their voice again. These are conscious experiences. Without them, what is there to life? In this sense, we all know what consciousness is – there's nothing we know more intimately – yet it remains one of life's greatest mysteries. Despite the incredible advances made in physical science, it doesn't seem like we're any closer to an explanation of where consciousness comes from. How is it, exactly, that the brain's 86 billion neurons give rise to conscious experience? As we'll see, our answer to this question will not only shape our understanding of the human mind, but the fabric of reality itself. – Extract from Philosophers on Consciousness