Frequent references to a "post-secular" world remind us that the "secularisation thesis" of an irreversible displacement of religious belief and practice in cultures shaped by science and technology is overly simplistic and has not been realised in many contexts. In this paper, I shall revisit the secularisation thesis, taking as a test case the science that has arguably provided the most potent rhetorical resources for challenging spiritual interpretations of the natural world, namely chemistry. In striving to manipulate matter and transcend the constraints of a supposedly optimally-ordered world, chemists like Joseph Priestley shifted the focus of human attention from spirit to matter, aiding the construction of a secular rhetoric. Yet as Charles Taylor has argued, there are deeper causes of the secularisation of western societies than the social effects of such changes alone and there is a need to distinguish the secularisation of science from secularisation by science. There is, therefore, a mythology to be exposed along with its attendant falsehoods, not least among which would be the claim that an effective substitute for religious adherence, conferring meaning, identity and purpose for a human life, has been or ever could be rooted in the sciences alone.