で as an Agent Marker


I read a study that listed the Agent Markers in Japanese as Ga, Ni, Kara, and
De

I currently have this understanding of agent marking in Japanese:

GA = Active Sentences NI = Passive Sentences DE = ? KARA = Passive (No
Physical Contact)

Can anyone fill me in on when exactly De marks the agent? I've definitely
heard it before, but I have no idea why it is being chosen over the other
options.

Agent marking just being the one actually doing the action.




で covers a broad range of circumstances under which some action is taken or
some event happens, including but not limited to place, means, and cause. You
can understand this で as denoting one concerning the people involved in the
action (as agents). These are usually a group of people. You can say 私達でする but
not 私でする. You can say 私の方でする but this should be understood as "my side" as
opposed to other parties although 私 may be the only constituent of that
"side".

The difference from が is it's still about a circumstance, or condition,
surrounding the action and doesn't answer the question _who does it?_ as
directly. The question it answers is more like _involving whom?_ or _under
whose responsibility?_. Probably for this reason it has no sense of exclusion
unless the existence of an opposing party is assumed as in scenarios where
division of responsibilities is at issue. 私の方でする is one such example, and it
practically means the same as 私がする (not anyone else). 皆でする excludes no one. In
contrast, 皆がする excludes anyone who falls outside of the boundaries of 皆,
sometimes even 私, because it specifically answers _who does it?_

