I've never heard of "social combat" before. Is it basically just arguing?
It can be, but it is more commonly called debating and sometimes bartering. I think a more appropriate term is verbal combat, though adding "combat" to the term in either case may cause some confusion.
In a couple of games I have played you can use social combat to talk someone into or out of doing something. A good example are hostage negotiators or suicide prevention people.
Social combat can be used to avoid physical combat in some cases. I know that this is usually done with one roll in HARP and RM as it is in just about every other older RPG out there. But this adds the idea of role playing the debate out much like a normal combat would be done where you can slowly reduce the opponents resolve down to the point they give in. It can add some intense moments to a game session involving only verbal interaction.
The idea of social combat is to add more role play to a RPG session and it can make for some really good and interesting game sessions without having to include actual physical combat.
Imagine if a party trying to get within a stronghold of some kind were able to simply talk their way past the guards instead of killing them, maybe even convincing them to help without the need for a charm spell or something similar.
Note that sometime in the next week I will be clarifying rules somewhat. I will hitting on things like what attacking the different stats means and possibly how one would go about it.
For example; Attacking the reasoning of your opponent may mean you are arguing against the logic they are using to stand their ground. Attacking their Insight may mean you are arguing against what they understand about the situation. Attacking their Will RR may include some kind of intimidation and making them believe it is just not worth trying to convince you to their point of view. Attacking their Presence may actually be used to raise up an audience against your opponent or even attacking their own self esteem. I may add Self Discipline to the list as it seems like it could fit with social combat.
Note that this may even become a submission as either an article in the Guild Companion or possibly the Guild Adventurer. I'll see how far I get in this next week while I am off from work.