Nagel sets out, as he says "not so much to argue against reductionism as to investigate the consequences of rejecting it - to present the problem rather than to propose a solution".In doing this he bravely challenges many of the givens of modern thought, especially scientific thought. He identifies three areas - consciousness, cognition and value which he claims a purely physically derived understanding of the world cannot explain. He accepts science will go on to explain many things it has not yet explained, but his key point is that we should not assume that physical reductionism will ever provide all the answers, (in this he includes the current formulation of Darwinism). And in not being able to provide the answers he argues we must re-think our whole approach to understanding the world. This is a short book, densely argued, and sometimes a bit repetitive. I suspect it will become regarded as an important book. Like any really interesting argument, you may completely disagree with it, but it is still worth reading.