  The details of the cascades of gene activations and deactivations have been investigated experimentally. Weber's and Rosenberg's summaries of the results indicate that biologists can explain initial pattern formation in terms of successive concentration gradients that regulate genes without essential appeal to information concepts. Weber brings this point home by arguing in detail that the use of the term ‘positional information’ is metaphorical and that the action of the bicoid gradient can be explained without the concept of information. He concludes that this gradient and others do not carry information in an intentional sense; rather, they play causal roles in the formation of new gradients through the regulation of genes.