This discussion of the structure of the brain implies its main and most mysterious property: it is conscious. Since consciousness is the only thing of which we are directly aware, it is massively important. Indeed in this book I make the bold claim that the unconscious mind is essential for consciousness: to be conscious at all, you need an unconscious mind. The unconscious mind is, in my view, one of the most important hypotheses of the 1900s. No matter what the unconscious mind does, or what information it may hold, or where it may be, it plays a vital role in human life. The unconscious mind may have been first imagined by the great Frederick Myers, who was such a notable early figure in the Society for Psychical Research, but it was greatly developed by the psychiatrists Sigmund Freud and Carl Jung. Most psychologists regard it as existing somewhere in the brain; yet brain anatomists seem not to have identified any region of the brain which might hold it. This allows me to speculate that it may not be in the brain at all; indeed I can even imagine that parts 38of it occupy the non-material world outside our diving bell. That may help to explain why psychiatrists can only get at bits of it. We know nothing about its overall size or content.