This book seeks to understand what bring to pass the birth of modern physics by focusing upon the formation of the concept of force. This would be the first book to note the important role magnetism has played in this process. Indeed, the force between celestial bodies, before the introduction of the Isaac Newtonian gravitational force, is first introduced by Johannes Kepler by analogy with the magnetic force. Moreover, this book, by concentrating our attention on the magnetism, fully describes the developments and the recognition of the force concept during the Middle Ages. The detailed description of the Middle Ages and the Renaissance is a strong point of this book. By discussing and emphasizing on the role accomplished by the magnetic force, this book makes clear the connection between the natural magic and the modern experimental physics. This book will open up a new aspect of the birth of modern physics.