In the Origin, Darwin explained that he used the term “chance” variation only to signify his (and others’) ignorance of the process by which new traits arise. In an enthusiastic review of the book, Asa Gray suggested a friendly amendment: that as long as the cause of variation was unknown, it should be attributed to God. Gray’s idea was that God had arranged for particular traits to arise in particular lineages at particular times, to be subsequently accumulated by natural selection. Before Gray’s suggestion, Darwin had hoped that evolution by natural selection might be viewed simply as God’s way of making new species. But in reflecting on Gray’s suggestion, Darwin realized that reconciling evolution by natural selection with any sort of conventional theology was going to be much more difficult than he had imagined (Figs. 16.1 and 16.2).

On the one hand, unless God arranged for just the right traits to arise in just the right lineages at just the right times (as Gray recommended), then evolution by natural selection would not guarantee the existence of any particular evolutionary outcomes, humans included. And surely humans were the end of Creation, no matter what the means. On the other hand, this way of making species required an awful lot of trouble on God’s part. Evolution by natural selection initially seemed like such a simple way for God to proceed: he only had to establish a set of laws (to govern population growth, inheritance, etc.) and then sit back and wait for species to make themselves, rather than creating each one separately. But the degree of divine guidance that Gray suggested – presumably for each and every species, not just humans – was as much or more trouble than special creation. Indeed, it was just a complicated form of special creation.