This article is a translation into english of a lecture given by paneth in 1931. The content of the work is described by the section titles: (1) the need for epistemological clarification of the fundamental concepts of chemistry, (2) the concept of substance in chemistry, (3) the epistemological standpoint of the ancient atomists, (4) the epistemological position of the concept of element introduced by lavoisier, (5) the double meaning of the chemical concept of element: 'basic substance' and 'simple substance', And (...) (6) the double meaning of other chemical concepts. Sections (4)-(6) are published in the following number of this journal. (staff). (shrink)