In 1867, George Campbell, Duke of Argyll, had published The Reign of Law, a book that Darwin found deeply annoying. A supporter of Richard Owen, Campbell argued that while evolution (or "Development") might be observable in the fossil record, it was merely evidence of God's purpose. God, for example, would cause horses and oxen to evolve in time to meet human needs. The brightly colored plumage of birds, Campbell went on, were simply God's decorations of nature for humanity's enjoyment.

For Paley, a watch is purposeful and thus must have been created by a being with a purpose. A watch needs a watchmaker, just as a world needs a world-maker—God. Yet both Wallace and Paley might have heeded the lesson from Voltaire's Candide (1759), in which Dr. Pangloss, a professor of "metaphysico-theology-cosmolonigology," through reason, logic, and analogy "proved" that this is the best of all possible worlds: '"Tis demonstrated that things cannot be otherwise; for, since everything is made for an end, everything is necessarily for the best end. Observe that noses were made to wear spectacles; and so we have spectacles. Legs were visibly instituted to be breeched, and we have breeches" (1985, p. 238). The absurdity of this argument was intended on the part of the author, for Voltaire firmly rejected the Panglossian paradigm that all is best in the best of all possible worlds. Nature is not perfectly designed, nor is this the best of all possible worlds. It is simply the world we have, quirky, contingent, and flawed as it may be.