  Here Darwin is noting that, though to speak of ‘chance variations’ may seem to be citing chance as the cause of the variations, in fact it is simply acknowledging that they ‘appear to have no assignable cause’.  But it is important to keep historical context in mind here. Whether Darwin himself ever flirted with the idea of ‘directed’ variation or not, he was acutely aware of two views from which his needed to be distinguished, very different from each other, but both holding to the view that variations arose for a  purpose.[11]  The most widely shared alternative was that found in natural theology. To quote the Reverend William Paley’s Natural Theology, regarding a beautiful instance of adaptation: “A conformation so happy was not the gift of chance”.  Likewise, among Darwin’s followers, the American botanist Asa Gray, in an essay entitled ‘Natural Selection and Natural Theology’, uses the same contrast to advise Darwin against the notion of ‘chance variation’: “…we should advise Mr. Darwin to assume, in the philosophy of his hypothesis, that variation has been led along certain beneficial lines.”