When I was trying to get a feel for the Wheel of the Year, I found the work of Janet & Stewart Farrar very helpful, but nevertheless not completely satisfying. Then, I was surprised to learn that the reason there are eight Sabbats is not because they are naturally occurring, but because Gerald Gardner wanted more holidays in the year and borrowed names for the same basic holiday from different cultures in order to get them.
Clearly, people find meaning in an eight-Sabbat Wheel; but a number of years ago I stumbled onto something that I think makes a lot more sense.
The Wheel supposedly represents the transitions of the natural world as well as human beings; the life-cycle of the God is reflected in the transitions of human life. I wasn’t looking for it in this context; but in Raven Grimassi’s first book, Ways of the Strega, there is a line from the lore that reads, “For there are three mysteries in the life of man which are: birth, sex and death (and love controls them all)." Eureka! It’s the four “major” Sabbats: Imbolc (birth), Beltane (sex), Lammas (death) and Samhain (love, or spiritual ecstasy).
This makes a lot more sense to me.