Unthinkable: Could we make a computer trip on acid?

For such a vital human capacity, consciousness is still a mystery to us. The question "What is consciousness?" has long been explored by philosophers but traditionally shunned by scientists, "because it was considered'spooky' or too vague or new-agey", according to author Andrew Smart. But that is starting to change, with neuroscientists and theorists in artificial intelligence joining the quest to locate what might be called the defining characteristic of humanity. Smart's new book Beyond Zero and One: Machines, Psychedelics and Consciousness puts forward a tantalising hypothesis: that consciousness is a type of hallucination that may have evolved through the aeons as a survival mechanism. To answer the question "What is consciousness?" one must imagine how a computer could become human, he says.