Random thought that occurred to me about spell memorization and spell-books in D&D. As we all know, the traditional way of doing it requires that Wizards “memorize” their spells each day and they require access to their spell book to do it. The whole thing, while probably motivated by game-play aspects of limiting wizards and making them make strategic choices, is clearly influenced by the way magic works in Jack Vance’s Dying Earth books where the spells are some kind of alien math that are “so cogent that Turjan’s1 brain could know but four at a time.” So when GMs are looking for a rationalization for the weirdness of it, that’s usually what they reach for. GMs and players too bothered by the weirdness generally remove the spell books entirely, so that spells learned are permanently known, and limits on how many times they can be cast are approached another way, such as by spell points or “slots.”
But what if it wasn’t that the spell, forcibly impressed on the wizard’s puny human brain, is magically erased when cast, but rather the formula such as the words, gestures and intonation that need to be used are so complex to figure out they require a concordance of astrological and mystical tables and a whole bunch of long-hand calculations such that you have to have your reference book and a fair bit of time to do the calculations before you can next cast the spell? What if you needed to know the exact date you are going to cast the spell to have any hope of solving the formulas and doing the look-ups to succeed. What you’re memorizing is that day’s solution once you’ve calculated it, and you don’t literally forget it, but it’s no longer of any use once you’ve cast the spell (because the formulas also depend on whether you’ve already cast it that day or not). Maybe you can’t just sit down and re-memorize the spell even if you’re carrying the book because doing so at any other time than the specific time in the morning the tables were compiled for is just too complex for mere mortals.
This seems like a good explanation for why the spell-book of a 1st level Magic User with only one spell (if you’re using Basic D&D/OSE by-the-book) is still a hefty tome but a higher level wizard with dozens of spells doesn’t require a library in his backpack. The bulk of the volume is the charts and concordances necessary for all spells, while the specific constants and formulas for any given spell are comparatively slight. That would also explain why a scroll is just a single sheet of paper but that can be enough to add a spell to your book (assuming you’re using that common convention). If you allow Magic Users to keep a spell memorized until they cast it, you could easily tweak the assumption to be that it’s the day that you sit down to memorize the spell that needs to be worked into the calculation, not the day it’s going to be cast.
I kind of like this for a more down-to-Earth explanation of most of the odder features of the traditional D&D spells system. It’s not that I particularly object to spells as alien mental constructs as much as that definitely flavors the world in a particular Dying Earth way, and I don’t always want that flavor in my setting. Now, if you really follow the logic of the rationalization, it does have some implications that are slightly different from the by-the-book traditional method…like you might be able to memorize a spell and keep it around if you did the calculations to be able to cast it on a specific future date. You could, of course, patch that by saying the calculations get too complex more than at most a day in advance, or you could roll with it. Maybe you don’t dare take your spell-book along, but you believe you won’t have to use certain of your spells until you reach your destination three days hence. I think that might be an interesting consideration for a wizard.
1- Turjan being one of Earth’s mightiest magicians in those latter times.