せいで, when to use and not to use it


Hi^^ I'm studying the usage of せい and せいで, and it says (I'm using "Dictionary
of Intermediate Japanese Grammar" as main reference) that it cannot be used to
express a reason :

> 1)宿題がたくさんある *せいで パーティに行けない。  
>  2)誰も手伝ってくれない *せいで 一人でやらなければならない。

(in both cases it uses から・ので・ために)

I'm not clear on these sentences: can't we consider the presence of a lot of
homework as a cause for not having time? [or is it related to the fact that
maybe homework are a "controllable" thing? ] what is the difference between
n°2 and, say, 私のせいで作業が遅れてしまった。[other than the past tense]?

I would really appreciate if you could also give me some other examples of
sentences where I can't use it. Thank you in advance.




Your book is correct on this if it explained the exceptions.

Even though quite a few of us native speakers DO use せいで to express reasons,
it is certainly not a recommendable use of the word in many cases. This is
because if you use it to express a reason, you will sound like you are blaming
someone/something in a harsh way instead of objectively analyzing the reason
for something. It could make you sound unnecessarily upset or, in some cases,
as if you were cursing.

Regarding your sentence 「私のせいで[作業]{さぎょう}が[遅]{おく}れてしまった。」, it is no problem to
say it because it is yourself, not another person, that you are blaming for
the delay.

Examples where one should avoid using せいで :

「[雨]{あめ}が[降]{ふ}ったせいでピクニックに[行]{い}けなかった。」

「[鉛筆]{えんぴつ}が[短]{みじか}くなったせいで[宿題]{しゅくだい}ができなかった。」

「[日曜日]{にちようび}のせいで[公園]{こうえん}に人がたくさんいた。」

