My understanding is that in order to qualify for the feat, you must have the prerequisites. However, this leaves the definition of 'you' a little unclear as any boost you might have by a magic item would theoretically change 'you'.
I think the answer can be found in the fact that with a headband of intelligence, you won't get extra skill points because of the bonus. In effect, your 'base' ability is what is being used to calculate the effects when increasing levels.
However, if you have Combat Expertise (Int 13 prerequisite) and have a headband boosting you to 15 INT, then taking a negative level doesn't mean you lose the feat - you simply needed a 13 INT to 'get' the feat, and when you take ability damage that takes you below it, you can't "use" the feat.
Short answer:
Your Dwarf will not be able to get the feat for which his (unenhanced) stats do not qualify him for.
Well, I don't think that a temporary stat is able to fulfill the feat prerequisite, so, I have no answer about spell's bonus. But if you read the description of any of the +X Stat Bonus Items in PFRPG you'll find that the stat bonus is temporary only for the first 24 hours of use (thus, you'll have to take your amulet to the bath). So, in case of items, it's allright to fulfill the prerequisites. But you'll lose acess to the feat for 24 hours after take off and put on again the item.
Aye, sorry my also bad english.
I'd be hard pressed to find it, and I'll look in a moment.
But, the generally accepted rule is that a temporary stat boost counts as a permanent stat boost if it is maintained for at least 24 hours. After that, the modified stat is considered the characters stat for all prerequisite purposes. However, if the character should lose the stat increase, the character loses anything s/he does not qualify for anymore.
So, the Dwarf in the example can take the Improved Two Weapon Fighting feat, if the amulet of Dexterity has been worn for at least a day continuous, but wouldn't be able to use the Improved Two Weapon Fighting feat if s/he isn't wearing the amulet.
EDIT:: Well, Page 388 of the Pathfinder Beta goes into temporary, and permantent stat bonuses. Under the title Ability Score Bonus, the first paragraph details temporary, and the last paragraph after the description of individual attributes details permenant. It doesn't state you can take a feat though, so I'll try and find a better example of that.
(Interesting note: It seems you can gain more skill points this way.)
EDIT 2:: I can't find anything that states explicitly that you can take feats. Perhaps someone with more patience than me will do so.
It says right in the book:
A character can’t use a feat if he has lost a prerequisite.
This doesn't directly answer the question about whether you can learn a feat with a temporary ability modifier.
However, based on this, I would readily rule that if you can sustain the temporary ability long enough to learn the feat, then you can learn it.
But, when that temporary ability modifier goes away, you can no longer use the feat - you still have it, but cannot use it.
Some DMs let you learn a feat in the amount of time it takes to write it on your sheet.
Other DMs make you find an instructor, train for days or weeks, practice, practice, practic.
Most are somewhere in between.
Me, I don't let anyone level up, or learn new class abilities, or gain feats, unless they have a day to work on them. I assume the weeks leading up to gaining this level have been trainging and practicing and perfecting these new abilities/feats, and this final day of concerted effort brings it all together.
So in my game, my answer would be, if you can sustain thta temporary ability bonus for the day of training, without it ever dropping, then you can learn the feat.
But if you want to keep using the feat, you better make sure to always have that temporary bonus, or find a way to make it permanent, because without the bonus, the feat is just wasted space on your character sheet.
It says right in the book:
Me, I don't let anyone level up, or learn new class abilities, or gain feats, unless they have a day to work on them. I assume the weeks leading up to gaining this level have been trainging and practicing and perfecting these new abilities/feats, and this final day of concerted effort brings it all together.
So in my game, my answer would be, if you can sustain thta temporary ability bonus for the day of training, without it ever dropping, then you can learn the feat.
But if you want to keep using the feat, you better make sure to always have that temporary bonus, or find a way to make it permanent, because without the bonus, the feat is just wasted space on your character sheet.
Agreed,
I usually let someone train over time from about half-way through the level to the end. So, if someone get's a +2 gloves of Dex, and never take them off from halfway through the level to the next level, then they can use that dex to qualify.If they lose that dex for any reason (got gauntlets of ogre power, gloves got eaten up by black dragon breath) then they can't use the feat, they no longer qualify for it (or any feat it's a prereq of!). it's very dangerous to learn a feat off a boost item.
I do, however, allow someone to retrain a feat. To do it, they have to declare they are retraining it just before they level. Then, they spend the entire next level NOT USING THAT FEAT, ever, not once. I usually have them erase it from their sheet. Then, when they hit the NEXT level, they can learn a feat in place of the one they lost. Works very well, and makes sense to some extent. I know I've forgotten skills I had in college, when they were very important. Obviously, they can't retrain a feat that's a prereq for another feat (although, they could retrain both feats over two levels, first the dependent feat, then the next level, the prereq feat).