Are in vitro tests suitable for regulatory use?

George E.P. Box, "Robustness in the strategy of scientific model building", 1979. This quote from George Box was the title of a book chapter on mathematical models-exactly the type of models which we will not address here, although a lot of the general reasoning can as well be translated to them, especially because they depend on the input and thus on the limitations of either in vitro or in vivo data, when applied for regulatory toxicology. This article was prompted by the 2008 SOT/EuroTox debate (March 2008 in Seattle and October 2008 in Rhodes), which challenged us in an Hegelian approach as thesis and antithesis to present with changing roles on both occasions on the statement " In vitro tests are useless for regulatory use." Here, we would like following Hegel a summary of thesis and antithesis, but also try to outline the synthesis.