[Pixelmancer]

Sidenote: Does Astral Combat actually require astral projection, or is it simply combat on the Astral? I can imagine an Adept who wants to be able to punch astral observers in the face.

♫ When my fist! Hits your face! ♪ And your face! Hits the floor! ♫

I was under the impression that astral combat required being projected and that adepts had to use dual natured weapons like a weapon focus or killing hands, but I could be wrong.

[JackVII]

When astrally perceiving, you become dual-natured (meaning you have presence in both the physical and astral planes simultaneously) and can interact with astral objects, including through combat.

Looks like you can. I guess the main limitation then between perceiving and projecting is ease of movement.

[Michael Chandra]

On the upside, punching an astral Shedim in the face doesn't let him take over your body.

[Kanly]

I figured that with perception you can shift over to the astral, but you cant really move around except for purposes of self-defense when attacked (so you're not "rooted").

[Namikaze]

I figured that with perception you can shift over to the astral, but you cant really move around except for purposes of self-defense when attacked (so you're not "rooted").

Astral Perception is a lot like AR.  You see both the physical world and the astral plane.  You can only move in the physical world though.  For astral planar movement, you'd need Astral Projection.

[The Bald Man]

I don't have my book in front of me but I recall some text about burned out mages and what happens to their skills...something along the lines that they become knowledge skills. 
Not sure if that helps with the discussion, but it is another data point. 

[Linkdeath]

And I believe that any skills, even ones which are not "available" to a character are instead available as knowledge skills. You may not be able to act on the knowledge, but you know all about it in theory. You know, like armchair detectives.

Just my thoughts.

[Namikaze]

I also do not have my book handy to provide a citation, but IIRC all active skills can be used as knowledge skills for the purposes of determining what your character knows about the topic he/she is good (or bad) at.

[Michael Chandra]

Sole exception: Arcana does NOT become a knowledge skill when a mage burns out.

And yes, all active skills can be used as knowledge skills.

[The Bald Man]

Sole exception: Arcana does NOT become a knowledge skill when a mage burns out.

And yes, all active skills can be used as knowledge skills.

Why not?  Is there an active skill use that a mundane can undertake with Arcane?

[RHat]

Sole exception: Arcana does NOT become a knowledge skill when a mage burns out.

And yes, all active skills can be used as knowledge skills.

Why not?  Is there an active skill use that a mundane can undertake with Arcane?

Yes - things like formula design can be carried out by mundanes.  The only use for the skill I can think of that mundanes can't access is in initation.

[Michael Chandra]

Also, the rules state it.