A vital delusion is a belief that a person clings to as a manner of making their existence seem meaningful. It ‘vital’ in that when the delusion fails or is undermined, the individual immediately pursues another belief to take its place.
“G.K. Chesterton said, when people stop believing in something, they don’t believe in nothing, they believe in anything. It cannot be a coincidence that the decline in Christian worship in Europe has been accompanied by the rise in all sorts of other superstitions and cults, including those of Freud, Marx, and Gaia” (269, The Evolution of Everythiing)
The Evolution of Everything by Matt Ridley