Multi-classing Wizard Sorcerers and Their Spellbooks

[Nominrath]

I'm playing a MC Sor/Wiz and trying to figure out my spell mix. I was wondering if I could copy one of my sorcerer's spells known to my wizard's spellbook (within the limits of copying spells as stated, of course) and thus prime the way for replacing said spell with later levels of sorcerer. Thanks!

[Iguanodon]

A sorcerer's spells aren't written down since a sorcerer's magic is innate rather than learned. You can only copy a spell which is already in writing. Therefore, you cannot transcribe a sorcerer spell.

You could copy rituals from your Tomelock book or Ritual Caster spellbook if you wanted, but not from a class which doesn't write their spells down.

[Sigreid]

I would consider giving you a huge head start on researching one of your sorcerer spells as a wizard spell but you would still have to put considerable effort into understanding what your doing well enough to map it out and create a usable recipe.

[Drackolus]

The "replacing your book" passage says you can copy down spells you already have prepared. Wording is vague enough to be up to the DM. Considering the passage itself, it seems clear that that was meant for wizard spells, but most ability passages don't seem to be written with mutliclasses taken into account. It honestly boils down to if your DM feels it's fair/logical. Essentially what you're really asking is: "When a Sorcerer casts Web, is it basically the same process as when a Wizard casts Web?" The fact that they go as far as to require the same components leans towards yes, but the fact that they rely on different ways of looking at it suggests no. Then again, if two people come to the same correct answer in different ways, they're still right. And someone who is good at two different ways of coming to that conclusion can work through a problem one way, then work backwards the other way. But there's nothing in-book that actually says any of that: that's completely my interpretation, because the book says nothing.
As far as balance goes, I don't think it really changes much. Wizards are expected to find at least some spells I think, and being able to choose two per level means they probably won't be hurting for too many anyway. Now, if you're a cleric/wizard and trying to copy over every cleric spell that is also on the wizard list to your spellbook, that might become abusive... But multiclassing spellcasters hurts enough that it's probably not going to make that character match up with a single-classed version of either class, so I don't see the real harm.

[Nominrath]

Thank you for all your replies. The reason I ask is because, while I understand why a DM might not allow a straight transfer, there is a kind of loophole that can be used to do this. Essentially, a sorcerer could create a spell scroll of a spell that is shared between the wizard and sorcerer lists and then a wizard could use that scroll to copy that spell into their book. Because, according to the spell scroll copy rules as stated under the Spell Scroll entry in the DMG "a wizard spell on a spell scroll can be copied just as spells in spellbooks can copied", which seems to refer to a spell that is on the wizard spell list, not necessarily a spell scroll created by a wizard. Given that, I suppose the real question is: Would it be unreasonable to eliminate this intermediary step of creating a spell scroll and allow a MC Sor/Wiz to copy a sorcerer known spell that is also on the wizard spell list into his wizard's spellbook (with applicable spell copying costs and requirements, etc.)?

[SharkForce]

i'd allow it. even if someone "abused" it to maximum extent possible, they'd only be getting lower level spells, they'd only get maybe 2-3 spells per character level of other class that they take, and it still wouldn't be nearly as good as just taking a level of wizard in the first place and getting higher level abilities *and* knowledge of higher level spells *and* the ability to cast spells of a higher level.

i'm not super concerned that a level 4 wizard might take the next level in sorcerer to add a few level 1 spells to their spell list. it isn't remotely close to being as good as just taking a level of wizard and learning fireball instead.

[Drackolus]

Keep in mind that creating spell scrolls is not a standard option in this edition. It is only presented in the dmg as an optional rule and it isn't very fleshed out. Many DM's may not allow that either - it was, after all, very unbalanced in 3.x.