Why did Wilhelm Ostwald reject atomism for many years?

Wilhelm Ostwald rejected atomism for approximately 15 years primarily due to his commitment to positivism, which led him to reject theoretical concepts that lacked strict empirical foundations.1

His opposition was further driven by his development of "energetics," a metaphysical interpretation of the world based on the principles of thermodynamics. Ostwald believed that thermodynamics was the fundamental theory of science and asserted the primacy of energy over matter, viewing matter merely as a manifestation of energy. Because he held that scientific concepts must be grounded in observable empirical evidence, he viewed the atomic hypothesis as lacking such a basis during that period, leading him into intense philosophical debates with atomist colleagues like Ludwig Boltzmann. Ostwald eventually acknowledged the validity of the atomic hypothesis in 1909 following the accumulation of sufficient experimental evidence.1