Recently, I have finished the Great Silurian Controversy, a magnificent book about the nineteenth century arguments over the age of the lower Palaeozoic greywackes/sediments of Devon, and the creation of the concept of the Devonian. And reading The Lewisian: Britain’s oldest rocks by Graham Park, it occurs to me that this should perhaps be called, The Great Lewisian Controversy. It shares the same historical and scientific intentions, and the same grand sweep of scientific history, this time from the early twentieth century – namely, the exploration over decades of the geology of the Lewisian of northwest Scotland.