 Approaches that rule out or ignore non-genetic inheritance might be characterized as “monist” in their treatment of the question of the existence and significance of multiple inheritance systems. Monist tendencies may be traced back already to Wilhelm Johannsen’s work at the beginning of the 20th century. While Johannsen invented the term “gene” in order to remain uncommitted to a specific view about the material constitution of hereditary factors, both this term and the notion of “genotype” that he developed suggest a monist view of inheritance. This tendency was reinforced by molecular genetics and the replicator framework.