Clearly Treyvaud’s で from the previous post (about で as implier of causality) wasn’t pure causality. The girl was just taking a break from her story, so the invisible それ in front of the で refers to the entirety of the story so far. Not a specific cause and effect relationship per se.
A large part of で’s role comes as a conjunction, a transition between two thoughts. To a certain extent, で is always conjunctive – it connects two different phrases or ideas within a phrase by describing why something was done – and only the level of causality changes.
The clear English equivalent is “so.” It’s surprising how similar these are. Not only do they both act as conjunctions, but the level of causality they both imply also varies. So, to a certain extent, Treyvaud’s で is asking, “So now that you’ve laid out all this juicy conspiracy goodness, WTF mate? What happens next? What does what you’ve just explained lead to?” But in reality, it’s just a word that enables a smooth transition to the next thought.
You see this used a lot in spoken Japanese. If someone is telling a really long, winding story that, rather than resolving itself, continues to take turn after turn, that person and the listener could have the following conversation:
Which you could translate into English as:
L: So where the hell is this going?! Heh.
T: I’m about to fuggin tell you if you’d let me finish.
Maybe that’s taking it a bit far, but you get the point. You can imply all that good stuff by interrupting with a single particle, a smile, and a good laugh.
The other conjunctive role of で is when you use it to stack up clauses, mostly when speaking. For example,
会社が新橋で、アパートが国分寺で、通勤がちょっとつらい。My company’s in Shimbashi, and my apartment is in Kokubunji, so my commute is a little unpleasant.
To me, the “so” feels like it implies slightly more causality than the で after 国分寺. I believe in cases like the above, で is the gerund form of です, so you can continue almost without end as you can with verbs sometimes:
6時に起きて、シャワー浴びて、朝食食べて、家出て、電車乗って．．． I woke up at six, took a shower, ate breakfast, left my place, got on the train…
Keep your ears open for this で (and verbs in gerund form playing the same role) and I promise you’ll start to hear it more often. And the more you recognize it and what it is doing, the easier it will be to use it yourself. Now go forth and conjunct!