The one-line version
Wicca is a modern religion with older ingredients. Both halves of that sentence matter: it was assembled in twentieth-century Britain, and the things it was assembled from are genuinely old.
Wicca did not exist in medieval Britain
There was no organised pagan witch religion running underground through the Middle Ages. People accused of witchcraft in the trials were overwhelmingly ordinary Christians, usually poor, often women, denounced by neighbours. Treating them as secret Wiccans erases what actually happened to them.
What did exist: folk magic and cunning folk
Village practitioners, known as cunning folk, wise women or charmers, sold charms, cures, protective work and thief-finding across Britain into the nineteenth century. Their practice was Christian in idiom, practical in purpose, and is well documented. Some of it survives in Wicca as technique, not as lineage.
Margaret Murray and the witch-cult hypothesis
In the 1920s Margaret Murray argued that the trials had persecuted a surviving pre-Christian religion. Historians rejected the thesis, and it is not accepted today. It was, however, enormously influential, and modern Wicca was built partly on the assumption that it was true.
Ceremonial magic and Crowley
Golden Dawn-derived ritual, Freemasonry and the writing of Aleister Crowley supplied much of the structure: circles, quarters, initiation degrees, tools, and a fair amount of wording. This is the best-documented ingredient of the lot.
Gerald Gardner and the New Forest claim
Gardner said he was initiated in 1939 into a surviving coven near Highcliffe in the New Forest. No independent evidence supports it, and historians treat it as unverified rather than proven false. Whatever happened, what Gardner published afterwards was substantially composed from folklore, Murray, ceremonial magic and his own hand.
1951, carefully worded
The Witchcraft Act 1735 was repealed in 1951 and replaced by the Fraudulent Mediums Act. The 1735 Act had penalised pretending to practise witchcraft, chiefly aimed at fraud. Its repeal removed a practical obstacle to writing and speaking openly. It did not legalise a religion, and Wicca was not banned before it.
Doreen Valiente
Initiated by Gardner in 1953, Valiente rewrote much of the ritual material, cutting Crowley's phrasing and producing the version of the Charge of the Goddess most Wiccans use. She quoted the eight-word Rede publicly in 1964. She was also unusually honest that the material was recent, which is why historians trust her.
Gardnerian, Alexandrian, and outward
Gardnerian Wicca spread through initiation from the 1950s. Alexandrian Wicca followed in the 1960s under Alex and Maxine Sanders. Both lines reached North America, Australia and beyond during the 1960s and 1970s, where Wicca met a much larger counterculture.
Feminist and Dianic developments
From the 1970s, feminist Pagans in the United States built goddess-centred traditions: Z Budapest's Dianic witchcraft, and Starhawk's The Spiral Dance (1979), which brought activism and ecology into the mainstream of the movement. Some Dianic groups have since been criticised for excluding trans women.
Solitary and eclectic Wicca
Scott Cunningham's Wicca: A Guide for the Solitary Practitioner (1988) made self-taught practice respectable, and the internet finished the job. Most Wiccans today have never been initiated by anyone, and this is now the ordinary form of the religion rather than a lesser one.
The Burning Times myth
The claim that nine million witches were executed, and that they were practitioners of a surviving pagan religion, is not supported by evidence. Estimates for the European trials are generally in the tens of thousands. The real victims deserve to be remembered as who they were.