The meaning of the で in 勢いで

Question

For example, in utterances such as

その場の勢いで

This would imply that someone does something due to the influence of their surroundings at the time, and if they were to rationally think it over by themselves they wouldn't say or do it. But my question is about which function of で this is.

The two that I can think of are 動作・作用の行われる状態を表す or 動作・作用の原因・理由を表す, analyzing the words literally isn't any big help but I think that it's the first usage. Can anyone clarify this?

Edit:I have added the example

「その場の勢いで言っているだけだったら、後で後悔するぞ」
「勢いなんかじゃありません。い、いえ、半分は勢いかもですが」

Answer 1

You have the correct answer.

「動作{どうさ}・作用{さよう}の行{おこな}われる状態{じょうたい}を表{あらわ}す」

"Describes the situation in which a movement or action is taken."

is the usage here because in the sentence

「その場{ば}の勢{いきお}いで言{い}っているだけだったら、後{あと}で後悔{こうかい}するぞ。」,

「その場の勢いで」 is describing the manner in which a statement was made.

"If you are just saying it in the heat of the moment, you are sure to regret it later on!"

I find this question to be insightful because the other usage

「作用の原因{げんいん}・理由{りゆう}を表す」

"Describes the cause or reason for an action."

is actually a little bit like the correct one.

In 「勢いで + 言う」, however, 「言う」 is just not an active enough event to call it a cause-and-effect relationship. If we had another verb phrase instead of 「言う」 as in:

「爆発{ばくはつ}の勢いで、窓{まど}ガラスがすべて吹{ふ}き飛{と}んでしまった。」(The momentum of the explosion blew away all the window panes. )

then, you could say that it was the other usage (describing cause/reason).

(This is why I asked for more context in the comment.)