Multilevel Reality, Mechanistic Explanations, and Intertheoretic Reductions

In this paper I argue that the question of interlevel explanations runs against the old and thorny problem of the intertheoretical reductions. In order to find a clue as to the solution of this last problem, I shall distinguish, though only provisionally and ideal-typically, between two sorts of intertheoretical or interlevel relations, a weak and a strong one. This distinction, somewhat like a masonry falsework, will be at least in a sense removed, because both types of reduction cannot exist in their pure form. They are only idealised forms of reduction, ideal types between which we find an indefinite number of intermediate forms of actual reductions. In both cases, relating multiple perspectives to one another to better understand the subject-matter under investigation requires constructing a new, wider or deeper perspective. And in both cases, the question of interlevel explanatory reductions, just as that of intertheoretical ones, cannot be answered abstractly, by purely philosophical considerations, but only with reference to, and in accordance with, the practice of scientists and the history of science. This is true not only for physical, but also for biological theories, as I shall briefly illustrate by two examples taken from biology (the protein folding field and today\u2019s debate about cancer research)