First Lines of the Practice of Physic, authored by William Cullen in 1781, stands as a seminal work in the evolution of medical science. Cullen, a distinguished Scottish physician and chemist, crafted this text primarily for the students at the University of Edinburgh, aiming to provide a structured and comprehensive introduction to the practice of medicine. His approach marked a departure from traditional methods, emphasizing a systematic understanding of diseases and their treatments.​

The first volume delves into the foundational aspects of medical practice, focusing on the principles of diagnosis and treatment. Cullen introduces a methodical classification of diseases, laying the groundwork for what would later be recognized as modern nosology. He distinguishes between the proximate and remote causes of diseases, advocating for a deeper understanding of the underlying mechanisms rather than merely addressing symptoms. This perspective encouraged a more analytical approach to medicine, fostering advancements in medical theory and practice.​

Furthermore, Cullen’s work reflects the intellectual climate of the Scottish Enlightenment, a period characterized by an emphasis on reason, empirical evidence, and systematic inquiry. His teachings and writings influenced a generation of medical professionals who carried forward his methodologies and philosophies. The impact of First Lines of the Practice of Physic extended beyond Edinburgh, contributing to the broader development of medical education and practice in Europe and the Americas.​

Cullen’s First Lines of the Practice of Physic represents a pivotal moment in the history of medicine. By advocating for a rational and systematic approach to understanding and treating diseases, Cullen not only advanced medical science but also set the stage for future innovations in the field. His work continues to be a valuable resource for those interested in the historical progression of medical thought and practice.