  The distinction between active and passive elements is still not clear. Some examples are obvious: if 16 is assumed—on the basis of some arbitrary convention—as the atomic weight for oxygen, the atomic weight of hydrogen will necessary be 1.008. “This means that the ratio of the two weights is a passive element of knowledge” (1935a, IV.1). However, as an active element of knowledge Fleck indicates also “the mere use of alcohol in preparing extracts”, adding however that “the actual usefulness of such extracts is a passive one and therefore a necessary consequence”. He also writes that the concepts of chemical element and of atom are derived “from collective imagination”, but “the usefulness of these concepts in chemistry (…) is really independent of the individual knower”. The active and passive elements of knowledge are inseparable either historically or logically, and every statement can be divided into active and passive part.