Standard STEM courses, for all of their value, do not tend to include systematic lectures or treatment about the nature of the scientific method. This book aims to provide a wide reflection on the general principles of physics and explore the foundations of scientific knowledge as a whole. The author delves into the study of what lies at the basis of science in general, and physics in particular. Themes such as the relation between natural phenomena and mathematical language are addressed, highlighting the main hubs of conceptual development in science. The volume also examines the conceptual and practical instruments that have been progressively developed to investigate the nature of physics. Furthermore, the author discusses the importance of “scientific practice” within the scientific community, emphasizing its role in advancing knowledge and how it contributes to physics as a whole. Divided into three parts, each covering different aspects of physics and its foundations, the text, while assuming basic knowledge of physics and mathematics taught in university courses, is accessible to all STEM students, and will be useful for anyone looking to gain valuable insights into the nature of physics and the methods used to acquire knowledge in this field.