​The book Galen and Paracelsus by John Call Dalton, published in 1873, offers a comparative exploration of two pivotal figures in the history of medicine: Galen, the esteemed Greek physician of the 2nd century, and Paracelsus, the radical Swiss alchemist and physician of the 16th century. Dalton examines their contrasting approaches to medical science, highlighting how each shaped the medical practices of their respective eras and beyond.​

Galen, whose influence spanned over a millennium, adhered to the humoral theory of medicine, positing that health was maintained through a balance of bodily fluids. His extensive writings became the cornerstone of medical education in Europe and the Islamic world. In contrast, Paracelsus challenged these traditional doctrines, advocating for a more empirical approach to medicine. He emphasized the use of chemicals and minerals in treatment, laying the groundwork for modern pharmacology. Paracelsus’s rejection of Galenic principles was so profound that he famously burned the works of Galen and Avicenna, symbolizing his break from established medical thought.​

Dalton’s work delves into the lives and philosophies of these two figures, illustrating how their differing views on disease and treatment reflect broader shifts in scientific thinking. While Galen’s methods were rooted in ancient traditions, Paracelsus’s innovative approaches signaled the dawn of a new era in medical science. Dalton’s analysis provides valuable insights into the evolution of medical thought, showcasing the dynamic interplay between tradition and innovation in the pursuit of healing.​

Galen and Paracelsus serves as a historical lens through which readers can appreciate the progression of medical knowledge. By contrasting the methodologies and philosophies of these two influential figures, Dalton underscores the importance of critical inquiry and adaptability in the advancement of medicine. Their legacies continue to influence contemporary medical practices, reminding us of the enduring quest for understanding in the ever-evolving field of healthcare.​