Lamarck Contre Darwin, Reduction Versus Statistics: Conceptual Issues in the Controversy over Directed Mutagenesis in Bacteria

The purpose of this paper is to examine some conceptual aspects of the controversy over the possibility of directed mutagenesis in bacteria that has erupted since the publication of some provocative results by Cairns, Overbaugh and Miller [2]. The paper by Foster in this volume takes up more “empirical” issues, surveys the experimental literature, and offers occasionally different interpretations of the results. The conceptual issues that are important here occur at least at two levels, the first of which is, in a sense, metaphysical and the second, epistemological. First, the possibility of directed mutagenesis challenges the core of the current orthodox framework of evolutionary theory. Thus the sense in which mutations can indeed be “directed” is of considerable foundational importance to evolutionary theory. To the extent that such foundational issues are “metaphysical,” in the sense that they concern the most general and universal underlying features of the world explored by science, these conceptual issues properly belong to metaphysics. Second, much of the evidence on which the current controversy thrives is statistical evidence about the number of mutant bacteria. Experimental methods which rely on such evidence are non-reductive in the sense that they attempt to understand what occurs at a lower level—for instance, that within a bacterial cell—by making observations at a higher level—in the example, that of the cell.