In 1759 the British mathematician Francis Maseres wrote that negative numbers "darken the very whole doctrines of the equations and make dark of the things which are in their nature excessively obvious and simple". Because of their dark and mysterious nature, Maseres concluded that negative numbers did not exist, as did his contemporary, William Friend. However, other mathematicians were braver. They took a leap into the unknown and decided that negative numbers could be used during calculations, as long as they had disappeared upon reaching the solution.

Naturally Speaking: A Dictionary of Quotations on Biology, Botany, Nature and Zoology, Second Edition presents the largest compilation of published quotations on the natural world available so that readers can get a feel for the depth and breadth of natural history and the life sciences. The book contains the words and wisdom of several hundred scientists, writers, philosophers, poets, and academicians. The bibliography is useful for readers who want to search for more details about the quotations listed while the extensive author and subject indexes provide the perfect tool for locating quotations.