Susannah Gibson explains how a study of pond slime could cause people to question the existence of the soul; observation of eggs could make a man doubt that God had created the world; how the discovery of the Venus fly-trap was linked to the French Revolution; and how interpretations of fossils could change our understanding of the Earth's history. Using rigorous historical research, and a lively and readable style, this book vividly captures the big concerns of eighteenth-century science. And the debates concerning the divisions of life did not end there; they continue to have resonances in modern biology.