This chapter explores the critical interplay between practice and theory in the evolution of modern natural science, emphasizing how the bourgeois mode of production established essential conditions for scientific development. It discusses the transition from speculative to empirical thinking that began in the late fourteenth century, highlighting the necessity for modern science to ground itself in practical applications. The chapter delves into the ideological struggles between the bourgeoisie and feudalists, underscoring how these conflicts shaped the theoretical landscape. It critiques the limitations of traditional theories and the significance of empirical methodologies, particularly the analytical-synthetic method, in forging a scientific framework that transcends mere speculation. By examining historical figures and their contributions, the chapter illustrates the gradual shift towards a systematic understanding of nature, ultimately leading to the establishment of modern scientific principles.