 This brief recapitulation of the origins of molecular biology reflects themes addressed by philosophers, such as reduction (see  Section 3.1),  the concept of the gene (see  Section 2.3),  and experimentation (see  Section 3.4).  For Schroedinger, biology was to be reduced to the more fundamental principles of physics, while Delbrueck instead resisted such a reduction and sought what made biology unique. Muller’s shift from Mendelian genetics to the study of gene structure raises the question of the relation between the gene concepts found in those separate fields of genetics. And the import of experimental methods from physics to biology raised the question of the relation between those disciplines.