Has there been an official ruling on the definition of a "force effect?"
I can't find a definition anywhere in the book, and I know that we use common-sense and half-remembered 3.5 ideas of what they are in my group, but I would like to see an authoritative definition. Is there such a thing and my forum search just missed it?
A force effect is anything that states it is a force effect, or that deals force damage.
Okay, but do they "do" anything special? Do they have special traits like ignoring damage reduction or hitting incorporeal creatures, or is it just physical damage with a spiffy name?
I think it's just an energy type like fire, cold, acid, etc. Some things are more susceptible and less susceptible to different energy types. I think I read somewhere that incorporeal creatures are susceptible to force attacks, for example.
Okay, but do they "do" anything special? Do they have special traits like ignoring damage reduction or hitting incorporeal creatures, or is it just physical damage with a spiffy name?
There are only two things special about force damage, and one of those is really not a property of force damage in and of itself.
First, force effects affect incorporeal creatures normally (damage, terrain, whatever). This is stated in the incorporeal rules, I believe.
Second, and this is the sort of tangential one, very, very few things are at all resistant to force damage. Force damage will have full effect on the target 99.9% of the time. It is not subject to DR and the only creatures I can think of with resistance to force are Epic-level 3.5 splat book creatures (like the Force Dragon).