Discern source of magic

Question

My wizard tells me that she remembers reading something about being able to use thaumaturgy to determine the source of magic, but neither of us can find it in the book. How does this work, if it's possible, and where can I find it in the book?

edit- To give some more info. The idea is to be able to determine a physical direction of the source magic caster/s of a magic spell. This could be either during the casting of the spell or within a time period after the spell has been cast.

Answer 1

@Joe's has the right of it above in general applications, but since she wants to actually track it, I'd say it might actually be closer to Solve Improbable or Impossible Problems. Both uses of thaumaturgy are found on YW263.

• Solve Improbable or Impossible Problems is a simple action, and the rules state "If a spell effect does seem to fall easily into one of the other categories, go with this one". As the example is Harry Dresden's tracking spell, that's my justification for choosing this one.
• Provide Inaccessible Knowledge is a subset of the above action, and is handled as an assessment action (YW115). I'd personally use this if she was trying to understand the nature of the spell, rather than just track it to the source, per counterspell (YW253).

Answer 2

According to my reading, Dresden Files' thaumaturgy can be used to provide knowledge that would otherwise be inaccessible. I would interpret this as allowing the wizard to use thaumaturgy to gain knowledge about the source of a magic spell, and apparently I'm not alone in that interpretation. (See the Dresden Files wiki's description of the types of magic: http://dresdenfiles.wikia.com/wiki/Magic and this one-sheet reference page on thaumaturgy from dresdenfilesrpg.com: http://www.dresdenfilesrpg.com/wp-content/uploads/2010/03/DFRPG-Spellcasting.102-Thaumaturgy.pdf)

Answer 3

I do not remember any instance in the books when Dresden used thaumaturgy to determine where a spell came from. In Storm Front, it would have made the book really short if he could do it. Now, maybe it is because Dresden is rubbish at thaumaturgy and only he cannot do it but Molly could.

I would rule that if the spell did leave something physical then you could track the source. For example, a dagger appears in the target's heart killing them. Thus, there is a dagger, thus you can track where it "comes from". If not, then I would rule that it is not possible. So, if the above spell just burst the heart, though luck.

That said, the magical theory side of thaumaturgy could be used to determine what sort of spell, place, and physical components would be needed to achieve said effect. Dresden works out that you would need an isolated house tapping the power of storms in Storm Front. No magic there, just the theory of how magic works.