The word "agency" is often used to describe the ability of a human to act as an agent, or the ability of a system to act as an agent. Philosophers like Marx often focus on systems as agents, other philosophers (I am not well read) and sociologists commonly focus on individuals as agents. Debating agency is very fun, and can be done at all times in all places, since literally everything is an "agent" :) . How much free will does a given agent possess; how are an agent's choices constrained by the systems in which it exists and the tools it has available?
http://en.wikipedia.org/wiki/Agency_%28philosophy%29 http://en.wikipedia.org/wiki/Agency_%28sociology%29
Also there is an academic philosophy thread here that you might be interested in: http://news.ycombinator.com/item?id=4891502
> Debating agency is very fun, and can be done at all times in all places
Yes it is and yes it can! I can't count the number of times I've had to backtrack and explain the concept of agency when having discussions where I brought it up.