The publication of On the Origin of Species in 1859 was the culmination of more than 20 years of work by Charles Darwin, and the ideas he presented in it would lead to a fundamental change in the way we think about life on earth. Evolution was controversial at the time and now, as the bicentenary of Darwin's birth approaches in 2009, it remains the subject of bitter argument. As revolutionary as the theory was, it did not come out of thin air, but developed within the context of the scientific and philosophical thinking of the period. In order to arrive at a better understanding of the current debate, this book looks at key moments in Darwin's life and at the relevant aspects of the intellectual climate of the time which, taken together, would lead him towards the theory. It goes on to consider how evolution has developed, how its opponents have responded, and how the arguments between scientific rationalism and religious faith are much the same now as they were in Darwin's day.