 Philosopher Neven Sesardić, while not dismissive of developmental systems theory, argues that its proponents forget that the role between levels of interaction is ultimately an empirical issue, which cannot be settled by "a priori" speculation; Sesardic observes that while the emergence of lung cancer is a highly complicated process involving the combined action of many factors and interactions, it is not unreasonable to believe that smoking has an effect on developing lung cancer.Therefor, though developmental processes are highly interactive, context dependent and extremely complex, it is incorrect to conclude main effects of heredity and environment are unlikely to be found in the "messiness".Sesardic argues that the idea that changing the effect of one factor always depends on what is happening in other factors is an empirical claim, as well as a false one; for example, the bacterium Bacillus thuringiensis produces a protein that is toxic to caterpillars.