This paper investigates the interface between philosophy and biochemistry. While it is problematic to justify the application of a particular philosophical model to biochemistry, it seems to be even more difficult to develop a special “Philosophy for Biochemistry”. Alternatively, philosophy can be used in biochemistry based on an alternative approach that involves an interdependent iteration process at a philosophical and (bio)chemical level (“Exeter Method”). This useful iteration method supplements more abstract approaches at the interface between philosophy and natural sciences, and (...) serves the biochemical community to systematically locate logical inconsistencies that arise from more theoretical aspects of the scientific process. Initial cycles of this iteration process identify the in vitro–in vivo problem as a central epistemological difficulty in biochemical research. While previous attempts have generated ad hoc rules to mend the gap between chemistry, biochemistry and biology in order to justify in vitro experimentation, this paper concludes that in vitro experimentation is heavily based on chemistry and cannot derive definite statements about biological processes. It can, however, generate results that will influence the direction of future biological research. The consequence is that the relationship between in vitro and in vivo experimentation is more of a psychological or social one than of a logical nature. Apart from highlighting these inconsistencies in biochemical thinking (“problem awareness”), the Exeter Method demands an improvement of biochemical terminology that contains separate and unequivocally defined terms for in vitro and in vivo systems. (shrink)