Darwin's evolving identity: adventure, ambition, and the sin of speculation

Why - against his mentor's exhortations to publish - did Charles Darwin take twenty years to reveal his theory of evolution by natural selection?

In Darwin's 'Evolving Identity', Alistair Sponsel argues that Darwin adopted this cautious approach to atone for his provocative theorizing as a young author spurred by that mentor, the geologist Charles Lyell.

While we might expect him to have been tormented by guilt about his private study of evolution, Darwin was most distressed by harsh reactions to his published work on coral reefs, volcanoes, and earthquakes, judging himself guilty of an authorial '"sin of speculation.' It was the battle to defend himself against charges of overzealous theorizing as a geologist, rather than the prospect of broader public outcry over evolution, which made Darwin such a cautious author of 'Origin of Species'.