Indogenes said:
Any idea how or why so many different varieties of decks developed? On one internet site that was indicated in this thread, there are lists of 500 types of Tarot decks. Some seem to be variations of the original Rider-Waite design, but I don't know if there are any decks that are very different in design or concept from them.
One of the big reasons why different decks were created was because not everyone agrees with the symbolism and correspondences used in the Rider-Waite deck.
If you look at the four minor arcana suits in the Rider-Waite deck, they have the following elemental/directional correspondences:
East = Air = Swords
South = Fire = Wands
West = Water = Cups
North = Earth = Pentacles or Coins
There are many people who work magickal systems using these correspondences, but there are others (like me) who prefer to associated the element of air with wands, and the element of fire with swords. Having them switched the other way just doesn't make as much sense for me although I understand the reasoning people give for the association.
As a result, other decks have been created that use correspondences that vary from the Rider-Waite and other older decks. Some decks incorporate specific symbolism and correspondences that are used by particular magickal philosophies. For instance, the Thoth deck was designed by Aleister Crowley and illustrated by Frieda Harris specifically for use within Crowley's Thelemic magickal system. There are decks designed for students of all sorts of magickal philosophies.
Then, of course, there are decks that were created by people who felt inspired to do so. It is a big job but clearly one that many people have felt called to pursue. And so we have hundreds of different decks available to us today.
For someone who is just learning it makes most sense to stick with a standard deck like the Rider-Waite one because the majority of books out there which teach how to read the Tarot will be based on this standard. Once you're familiar with the basics you can research other decks and find one that has symbolism which more closely matches your own magickal philosophy. Or perhaps you'll be one of the people to create your own deck!