This book presents a long, multifaceted argument for pursuing universal biology in the face of (in William James’s colorful words) the “blooming buzzing confusion” offered by familiar Earth life to researchers. As Chapter 5 discusses, the central challenge for the program of universal biology is that familiar Earth life – the only form of life of which we can be certain – represents a single example and there are positive reasons for worrying that this example is unrepresentative of life. Biologists have discovered that life as we know it on Earth descends from a last universal common ancestor, and hence represents a single example. Moreover, biochemists have established that life elsewhere could differ from familiar life in certain ways at the molecular and biochemical levels, and they do not know how different it could be from familiar Earth life. Finally, as Chapter 6 explains, contemporary biological theorizing about life is founded upon what we now know is an unrepresentative form of familiar Earth life, namely, highly specialized, latecomers to our planet (complex multicellular eukaryotes). Indeed, a central theme of this book (Chapter 1) is that much of contemporary biological thought is still implicitly wedded to a defective, neo-Aristotelean, theoretical framework for life based on animals and plants.