Readying and action to disrupt spellcaster

[Sacril]

If a player readies an standard action to shoot at a spell caster when he starts casting a spell, will his action go off if the spellcaster "casts" silent Dimension Door; which only has a verbal component? Basically, how will he know to attack the caster if the caster doesn't do anything?

[Weirdo]

Because there's no rule saying you can't identify a spell without components, you can identify a spell without components (and thus counterspell or disrupt it).

This is usually interpreted as the spell gathering some form of visible magical energy - perhaps the caster's eyes glowing. At minimum the concentration involved in spellcasting would be apparent to anyone watching the target and waiting to disrupt their spell.

Developer comment from Jason Bulmahn

Jason Bulmahn wrote:

Hey there Everybody,

The rules here are certainly not clear, because they generally assume that the act of casting a spell has some noticeable element. Notice I did not say component, because I think the rules are silent on parts of spellcasting that are codified components versus those that occur without any sort of codification, such as the wiggle of a finger, change in breathing and other flavor bits that happen when a spellcaster makes the magic happen, as it were.

Back to the topic at hand, since the rules are silent here, I think it is well within the GMs purview to impose a penalty to the Spellcraft check to identify a spell without components (V, S, M). Since there is no real increase for spells with just one, I would guess that this penalty is not very large, perhaps only as much as -4.

This is, of course, up to your GM to adjudicate.

Jason Bulmahn
Lead Designer
Paizo Publishing

Edit: I should also note that I also agree with James, that a strict reading of the rules says you can make the check, without penalty, regardless of the spell's components.

[GM-JZ]

I agree. The components of a spell are very definite physical objects, movements or verbal enunciation. However, I have always played it that pretty much any spell has some kind of visible element or some change in behaviour of the caster that can be readily determined.

I'd allow the player the readied attack but I don't think the rules are explicit on it

[LazarX]

GM-JZ wrote:

I agree. The components of a spell are very definite physical objects, movements or verbal enunciation. However, I have always played it that pretty much any spell has some kind of visible element or some change in behaviour of the caster that can be readily determined.

I'd allow the player the readied attack but I don't think the rules are explicit on it

The rules on the silent and still metamagics make absolutely no comment on the ability to identify spells that are cast or noticing spellcasting actions.

Nor is there any commentary on spells which only have one component such as vocal only spells, or swift/immediate action spells such as feather fall.

[DM_Blake]

Since there are no rules saying that removing components makes it difficult to identify the spell or make an AoO or readied attack, you should allow the readied action. By RAW.

I explain it by saying that the components are only part of spellcasting. It still takes some amount of concentration to cast spells (the spellcasting chapter makes this quite clear). The identification, AoO, and readied actions are all triggered off that concentration as the caster focuses his mind on casting and momentarily drops his guard.

House rules are another story, as is clearly illustrated by Jason's quote above.

[felinoel]

...

I know how I am targeting spellcasters from now on, especially since one just feebleminded me the other day.