David Hume (1711-1776) was a Scots philosopher who developed empiricism in opposition to the continental Rationalism.  More than any other thinker of his time, perhaps with the exception of Immanuel Kant, he deconstructed the philosophical understanding of reason that provided the rational basis of the classical conceptions of philosophy and theology.  One of his most famous quotes in one of his fictional dialogs (his work was so “heretical” that he frequently used narrative to express his ideas to prevent censure) was that “reason marshals invincible arguments against itself”.  Hume’s scepticism about reason was such that Bertrand Russell in commenting on it said that for Hume, “there was no logical difference between sanity and insanity” and that the Humean sceptic would “still eat if they got hungry” even though their scepticism tells them they have no reason to.  Russell considered Hume as illustrating the bankruptcy of 18th century reasoning but many empiricists, pragmatists and positivists consider his arguments compelling, and his refutation of the argument from design has formed the basis of refutations of theism by some non-positivist, modern atheist philosophers such as Mackie and Flew (though Flew in 2006 became convinced there was compelling evidence for theism).

This short 1000 word essay deals well with his argument against the order observed in the universe as implying it requires a designer (God), a PDF is found here.