Like most/if not nearly all Neo-Pagan religions, Wicca is also a re-constructionist religion at it's heart. The difference comes in that Wicca has more than a healthy dose of romanticism added in - it's a key component of the religion. We have pantheism, polytheistic archetypes, traditional polytheism, nontheism, even polydeism beliefs. What all of these beliefs have in common is that they are adaptable and highly individualistic. Most of us do not worship the same God and Triple Goddess Gardner did. In this sense, Wicca is unique as the majority of the beliefs, regardless of what they are, tend to at least draw from the Jungian Archetypes so familiar to the human experience. Everyone has a mythology, be it stories of Luke Skywalker or Herne or Athena. This Archetype approach to theology, and the fact that it's highly individualistic, means that the Divine does not need to be real in the same traditional sense religions like Christianity use (how real the Christian god is is measured very differently then how real the pantheist's deities are.). It also means our own sense of romanticism towards the past, or the future, is what drives our connection to the divine. I've always liked to think of the re-constructionist revival in general as a coming home to our divine parentage, be it Nature or a specific deity like Athena, only now we're all grown up and can take responsibility for our beliefs. We take the best of the beliefs and strive to make them even better. This is a far cry from religions like Christianity that is fighting against it's own evolution and rejecting it's progression as heresy in some cases. From this standpoint, Gardner was really just one of the common foundations we us to kick-start our own beliefs, or more accurately, how we approach them. At the end of the day, there is no dogma thus our beliefs are merely our own, not Gardner's. He just helped give us the framework, especially for community. Much like developing a common language between covens and seekers.
Authenticity on Witchcraft -
All magic comes from an empirical root in the psychology we use to connect to our innermost selves and the divine. The Supernatural, or lack there of, nature to magic really doesn't matter in the long run. The magic I practice is different then the magic practiced by the next Witch in the room, so certainly my magic is also different than those witches that lived in Italy in the very late 1800s. Across cultures and across time, it all comes down to that common root. What Gardner provided was a common umbrella for those interested to find each other and compare notes. The need for authenticy is a hold over from Christian beliefs so embedded in our own cultural mindset, but it often forgets that Wicca is too a re-constructionist religion. We are trying to regain what was lost, and you can't do that without rediscovery. Traditions that claim to predate Gardner tend to also claim that they already had their discovery. Some traditions believe they have since found theirs. The rest tend to take the approach that we are still looking for it. But Wicca has a good amount of romanticism too, which means a lot of us are keeping our eyes open for new discoveries as well (the influx of New Age thinking for many witches, as much as it does annoy me on a personal level, is a good example of this in action). At the end of the day, I don't need absolute proof that Gardner stumbled upon the ancient Witch-cult that had organized itself (ha! Pagans organizing :p suuuure) to hide from the Inquisition. All I need is the framework to start my own journey of discovery of the Craft. It's a big Craft, a lifetime is not enough time so we all focus on the areas that are important to us. If nothing else, Gardner gave the world something undeniable: the permission to explore Witchcraft openly and share our discoveries there of.
Image of Gerald Gardner via Wizzley