How does fighting defensively work?

[Vincent The Dark]

So, it's a standard action and it can be a full-attack action. It sounds to me like it is something you add to the attack. In that case, can you charge and fight defensively at the same time (when you get there). Can you ready to an action to fight defensively? Do you have to be attacking to gain the bonus to AC? Can you add it to a spell?
I just don't get the full concept besides something similar to Combat Expertise.

[Grick]

Vincent The Dark wrote:

So, it's a standard action and it can be a full-attack action. It sounds to me like it is something you add to the attack.

Fighting Defensively as a Standard Action: "You can choose to fight defensively when attacking. If you do so, you take a –4 penalty on all attacks in a round to gain a +2 dodge bonus to AC until the start of your next turn."

Fighting Defensively as a Full-Round Action: "You can choose to fight defensively when taking a full-attack action. If you do so, you take a –4 penalty on all attacks in a round to gain a +2 dodge bonus to AC for until the start your next turn."

Vincent The Dark wrote:

In that case, can you charge and fight defensively at the same time (when you get there).

Charge: "Charging is a special full-round action that allows you to move up to twice your speed and attack during the action."

Charge is neither a standard action, nor a full-attack action, so you cannot use it with either method of fighting defensively.

Vincent The Dark wrote:

Can you ready to an action to fight defensively?

Readying an Action: "You can ready a standard action, a move action, a swift action, or a free action."

Vincent The Dark wrote:

Do you have to be attacking to gain the bonus to AC?

"You can choose to fight defensively when attacking."

Vincent The Dark wrote:

Can you add it to a spell?

Is the spell using a full-attack action or a standard action to attack? If so, yes. If not, no.

For example, you could fight defensively while delivering the held charge of a touch spell with an unarmed strike or natural weapon.

But you can't fight defensively while casting haste or bless.

[Daehsquinn]

Vincent The Dark wrote:

So, it's a standard action and it can be a full-attack action.

Yes, so you can't do other standard actions or move actions, respectively.

Charge: full round -> no
Readying: standard action -> no
Spell: standard action (most) -> no
fighting defensively and not attacking -> ok, because not attacking is no action EDIT: forget this one, Grick's answer is better

[Nefreet]

You can also Fight Defensively while Power Attacking and using Combat Expertise.

You probably won't hit anything, but you could always roll a 20.

[Eleos]

There is something called Full Defense that counts as a standard action and gives you +4AC http://paizo.com/threads/rzs2iepu?Full-Defense

And as for casting, you can Cast Defensively http://paizo.com/threads/rzs2jwup?How-to-cast-defensively

[Grick]

Eleos wrote:

There is something called Full Defense that counts as a standard action and gives you +4AC (http://paizo.com/threads/rzs2iepu?Full-Defense)

That's Total Defense.

Eleos wrote:

And as for casting, you can Cast Defensively (http://paizo.com/threads/rzs2jwup?How-to-cast-defensively)

Casting Defensively means you don't provoke an AoO, it doesn't increase your AC. It has no relation to fighting defensively.

[RtA]

One possible advantage for me (A Halfling Grenadier) at least is when charging with Charging Hurler while fighting defensively.... being able to rack up all your Dodge bonuses from things like Cautious fighter and so on, which increases your AC while only taking a -2 on thrown weapons like bombs

[Gallant Armor]

Nefreet wrote:

You can also Fight Defensively while Power Attacking and using Combat Expertise.

You probably won't hit anything, but you could always roll a 20.

That sounds like my gimpzilla that I came up with while bored:

Gnome Universalist (arcane crafter) wizard with 9 Int and 5 Str, all attribute points go to Cha
Fights with 2 broken medium sized swordbreaker daggers as one handed weapons without TWF feat or proficiency

Always fights defensively

Wears splint mail without proficiency

At level 20 this would add up to
10 foot move speed
-17 for main hand attack, -21 for off hand attack
If he hits he would do 1d4-5 damage