I go all over the place on this one. My gut tells me that we just haven't found (and may never find) the connecting thread. It might be a passion play, a star map, a poem, a novel.. something that would have grouped all of these things together.
Sometimes I think that they are just a random collection as Lorredan describes. Someone thought "Hey, instead of using one of the four suits, let's make a new one with special images", and grabbed what was nearby in the print shop, or cut them out of dad's library.
Sometimes I think that there was originally a larger group of images, one that had all the virtues, and more estates of man, and whatever else, and that some of these were removed as the game became defined.
Sometimes I wonder if they were like "Trading Cards". That at one point people were collecting and exchanging sacred images, on pilgrimages perhaps, or among tradesmen, and these are a collection from different "series", that were plainly just added on top as a group without meaning *as* a group.
For the most part, I "can" see a general estates-worldly experience-celestial estates design, but there are just too many little things that make me feel less than terribly confident about it. Why no Prudence? Why a Hanged Man? Why a Popess? Why an Empress? Why a Tower? I just think the story could be, and was, told with more common symbolism.
I can see logical groups.. The Virtues, the Sun-Moon-Star, the Angel and the Devil, Empress and Emperor, Pope and Popess. I can see Vices like Fortune, Foolishness. I can see Triumphs like Love, Death, Time, Eternity, and maybe even Fame and Chastity too.
So I wonder, what is the "thread" that could tie all of these groups together?
The Tarot will lose all its vitality for one who allows himself to be side-tracked by its pedantry. - Aleister Crowley