Page 455 - Makino,Tsutusi.DictionaryOfIntermediateJGrammar

sei 381
b. @&flb1& {a%% /CI)T/k@CZ/???+?L\Tl .tts$d:<
Ymso
(Because she is here, I can do a lot of work.)
Sei ka, however, is used whether the result is desirable or undesirable, as
in (2), KS(B), Exs.(c) and (d).
(2) a. %E&flbl&+?~\aWWd: < B%ao
(I think it is because she is here that I can do a lot of work.)
3 rv - .
b. $i&flx%$l1$%$~8~r:+?~\a~zg8&fl%d:o
3k~~lb:
a7k0
,
(Because the emission control rules have worked, I sup-
pose, the air has become cleaner than before.)
(tl)
(
c. ~&LE~;&o+?L\& ~Edsd: ts9 fi,
(I feel a little better after taking medicine, although it might
be my imagination.)
3. Sei de is used when the speaker finds the cause of an undesirable result
to be beyond his 1 her control, as in KS(A). Thus, if the cause is within
the speaker's control, sei de cannot be used, as in (3).

Sei ka has no such restriction as KS(B) and Ex.(c) show.
4. Sei cannot be used to express a reason. The following sentences are
ungrammatical.