These were volumes compiled by many wizards of the past, untidy folios collected by the Sage, leather-bound librams setting forth the syllables of a hundred powerful spells, so cogent that Turjan's brain could know but four at a time.
-Turjan of Miir
Today, the Dungeons & Dragons Legends & Lore column attempted to address the question of "Vancian Magic" in the world of D&D. As with everything Monte Cook writes, the Twitter-verse has been abuzz with discussion about it. After a lot of consideration, I thought it necessary to address my problem with the discussion and perhaps suggest a way for moving forward.
Jack Vance wrote a series of stories, beginning with Dying Earth. Although I have never read the story, I try my best to summarize the relevant features here. In this far-future setting, wizards spend time preparing a spell by preparing ritual components, gestures, words, and so forth. This prepared spell is magical and the discharge of that magical spell leaves the wizard without that power. He has expended it and the spell is gone from his memory. This process is so complicated that wizards can only prepare a handful of such spells every day. Say, perhaps four. Unlike the typical fantasy wizards, Vancian wizards' magical prowess was very limited. They had to rely on magical artifacts, combat prowess, and other skills to survive. It was a unique take on a fantastic concept, a take that inspired Gary Gygax when developing the Dungeons & Dragons system.
Although inspired by the writings of Vance, the D&D magic system began to become its own creature. Spells would be assigned to different "spell slots" based on power, so a wizard would have to choose to prepare a number of weaker spells despite his advanced knowledge and ability. Weaker spells would become more powerful (perhaps, as compensation for having to continue selecting them), but the overall direction was something different than the writings of Vance. Furthermore, wizards of high level would have 30 or 40 prepared spells, far beyond the "handful" envisioned by Jack Vance.
Eventually, Third Edition included the ability to augment or modify spells. A wizard could memorize his standard Fireball, or he could prepare a variant by using a "higher level spell slot." Where before, a wizard could only memorize a specific "formula" or version of the spell, the Third Edition wizard had the ability to move spells around to change their precision, power, and effect. Furthermore, certain magic-users had the ability to turn any previously prepared spell into a certain, basic magical effect (such as a cleric with his healing ability). Once again, the game moves away from Jack Vance's model and towards a uniquely D&D system of magic.
Fourth Edition changed the system again. Now, everybody had "utility belt" powers. Only the Wizard had any freedom to change what he loaded. Furthermore, even that ability was limited. Every class had only a small handful of such abilities, generally no more than ten. Arguably, this limited scope puts them more in line with Vance's "handful" of magical spells. However, they lost the ability to choose from a wider selection of spells. In total, many consider this distinction too far from the Vance model to still bear the name "Vancian."
It is worth noting at this point that this does not capture the full extent of magic within the D&D tradition. Other methods have been presented in various sourcebooks or articles. Furthermore, every group creates its own rules and variants that color the system. Through play, certain elements will become more iconic or important than others. This is perhaps the biggest wildcard in understanding what it means to be Vancian Magic.
The point of this brief survey is to attempt to determine it means to be a Vancian magic system. For some, it is the unique aspect that a wizard prepares his small handful of spells at the beginning of the day and, once used, they are unavailable. For others, it is the ability to look over a vast list of spells every morning and plan which to choose to have available. Some see the Vancian system as a means to limit the power of wizards, to keep them "balanced" with the other classes. Many see it as elements of all of these things. At the end of the day, what makes a magical system Vancian will depend on the perspective of the viewer.
The words "Vancian Magic" invoke any varied number of memories, feelings, and emotions in anybody who has played Dungeons & Dragons in the past thirty years. Everybody has different understandings, different memories, and different expectations. To have an intellectual conversation about the benefits and perils of Vancian Magic requires establishment of a fundamental understanding of what Vancian Magic really is.