Dawkins originally wrote the essay in 1991 and delivered it as a Voltaire Lecture on 6 November 1992 at the Conway Hall Humanist Centre.
The essay discusses how religion can be viewed as a meme - an idea which Dawkins had previously expressed in The Selfish Gene (1976).
The essay was later published in A Devil's Chaplain (2003), and its ideas are further explored in Dawkins's documentary television programme The Root of All Evil?
[2] Dawkins also describes religious beliefs as "mind parasites",[3] and as "gangs [that] will come to constitute a package, which may be sufficiently stable to deserve a collective name such as Roman Catholicism ... or ... component parts to a single virus".
Further Dawkins distinguishes this process from the spread of scientific ideas, which, he suggests, is constrained by the requirement to conform with certain virtues of standard methodology: "testability, evidential support, precision, quantifiability, consistency, intersubjectivity, repeatability, universality, progressiveness, independence of cultural milieu, and so on".