This book is a collection of readings about the nature of life. The idea for it was born when we first met and discovered our mutual interest in the nature of life, a shared background in philosophy of science and philosophy of biology, and a complementary scientific expertise in the origin of life and astrobiology (Cleland) and artificial life and synthetic biology (Bedau). We both wanted to have a book like this, so we decided to compile it together. Our interests and orientation led us to include material in four general areas: (i) classical philosophical and scientific discussions about the nature of life, (ii) contemporary scientific and philosophical discussions of the origins of life, and of chemical possibilities for unfamiliar forms of natural life, (iii) discussions of contemporary artificial life creations, including not just computer simulations but also self-reproducing robots, protocells, and other synthetic biology constructions created in the wet lab, and (iv) attempts by contemporary scientists and philosophers to describe and explain the nature of life in its most general, non-Earthcentric, form. Producing this book confirmed for us the value of combining multiple perspectives on life.

We hope that this book will inform philosophers about the latest scientific advances and introduce scientists to subtle philosophical puzzles and problems, and thereby foster new, well-informed and thoughtful philosophical and scientific reflection about the nature of life. In our opinion, genuine progress in understanding life crucially depends upon combining both scientific and philosophical perspectives on life.