In the past decade, Ray Kurzweil has also emerged as an advocate of technologies that offer prospects for dramatic life extension and increases in human capacities.

In The Age of Spiritual Machines (1999), he predicts the development of immensely powerful and fully conscious artificial intelligence. This, fortunately, will not compete with humans for mastery of the Earth.

Instead, we will merge with our mind-children, transcending many physical and cognitive limitations.

It will be impossible to be sure where cybernetically enhanced human beings end and advanced technological artefacts begin.

In The Singularity is Near, Kurzweil takes his vision further.

Our destiny is to create a vast sphere of intelligently organised space, expanding into the larger universe at the speed of light.

The key claim is that all known forms of complexity increase exponentially. If this is applied to the growing power of our technologies, we are now at the 'knee' of the curve. From our viewpoint, it will soon appear to climb towards infinity. As the 21st century unfolds, Kurzweil argues, humankind will gain practically infinite computational power, and our knowledge of how to employ it to transform ourselves and everything around us will follow.

Of course, he is well aware of the many arguments that can be put against his vision. Some opponents will find it implausible, arguing that there are always practical limits to growth; others will see his vision as politically or humanly undesirable. Kurzweil's counterarguments are formidable, but he doesn't seem to 'get' how alienating some will find his vision.

The Singularity is Near is a key addition to current debates about our future. It will attract legions of admirers - and opponents.