Can you take Magical Knack twice?

[Seiryu]

Trait - Magical Knack
"Benefit: Pick a class when you gain this trait—your caster level in that class gains a +2 trait bonus as long as this bonus doesn't raise your caster level above your current Hit Dice."

Are you able to take this trait twice, one time for two different classes, since the trait bonus applies to a specific class?

[SlimGauge]

No, at least in part because you're not allowed to have two traits from the same category.

Rules wrote:

Restrictions on Trait Selection: When selecting traits, you may not select more than one from the same list of traits (the four basic traits each count as a separate list for this purpose).

[Seiryu]

Well, that's a bummer. Thanks. I never knew that.

[Avatar-1]

It's also a "trait" bonus, which doesn't stack.

So if you find another trait from a different category that also gives a trait bonus to caster level, no dice.

[James Risner]

If you were not prohibited from taking it twice, and if typed bonuses were not prohibited from stacking you still wouldn't stack. Untyped bonuses from the same source won't stack. Two of the same trait are the same source.

[kestral287]

Did we really need two people to say that trait bonuses don't stack when that is addressed in the OP?

Seiryu wrote:

Are you able to take this trait twice, one time for two different classes, since the trait bonus applies to a specific class?

This is functionally no different from a +1 trait bonus to Will saves and a +1 trait bonus to Fort saves. It would affect two independent qualities, so if we had Magical Knack: The Religious Trait you could take both, so long as they were applied to different classes.

On topic: If it's a home game, 3.5 (I'd have to look up the book) has a feat called Practiced Spellcaster, which is Magical Knack but up to four caster levels.