This article is an attempt to present the critics that Galen made against ancient atomist theory based largely on his theory of elements. For Galen, the problem of irreducible complexity in nature can’t be explained by the atomist theory, especially when the issue is concerned with a metaphysical discussion in the context of philosophy of nature. Yet for him the subject of change in nature was not explicitly formulated by proponents of atomism. For this being the case, by criticizing atomism, (...) Galen tries to formulate a syncretic theory which is mostly an amalgamation of Aristotle and Hippocrates’ views. His theory is a frame in which like-elements affect the likes through a presupposed ‘leap’ between them that is largely related to krasis; which eventually makes the change, bodily sensibility and lastly the pain possible. Therefore, it is imperative that one embraces a transient theory like that of the combination of Aristotle-Hippocrates’s, instead of a closed-theory such as atomism. Taken into consideration from the point of philosophy of nature, Galen would come to the terms with a teleological causality instead of mechanical one. All combined, Galen’s mentioned understandings has led him to bring serious criticism against the atomist theory which can be seen as the extension of his medical-philosophy project. (shrink)