The old distinction between science as “pure” knowledge and technology as “applied” knowledge is too facile if used absolutely, but it has practical value. Johnson deals in both kinds of knowledge without discrimination: what led Darwin to the theory of natural selection is grist for his mill, but so too is what led Willis Carrier to invent the air conditioner. Yet it seems to me that there’s a difference between “good ideas” that lead to increased understanding of the world and the creatures in it, and the “good ideas” that are instrumental, that lead us to manipulate the created order for purposes that vary greatly in their character and value.