Thomas Reid (1710-1796) is best known as a moralist and as one of the founders of the Scottish Common Sense school of philosophy. He was also an influential scientific writer. This book is a study of Reid's most important papers on natural history, physiology and materialism. It surveys the extent of his scientific writings, illustrating the inter-relations between his scientific and philosophical thought, and redefines Reid's place within the Scottish Enlightenment. In a wider context, the book also raises questions about the role of science in the enlightened culture of 18th-century Scotland.