11

「食{た}べる」 can be negated as 「食べない」. 「美{うつく}しい」 can be negated as 「美しくない」. etc. etc.

Can you negate 「べき」as in:
「明日は受験なので、勉強するべきです。」(Since you are taking a test tomorrow, you should study.)
「明日は受験なので、遊ぶべき___。」(Since you are taking a test tomorrow, you should not play around.)

Every part of speech in Japanese seems negatable, but I can't figure-out how to negate 「べき」。「遊ばないべきです」 is not the answer I am looking for.

15

べき is a fun part of modern Japanese grammar with odd rules probably best explained using the historical explanation.

History

べし used to be a 助動詞{じょどうし} (auxiliary).

Connecting to things before it: べし followed the 終止形{しゅうしけい} (conclusive form) normally, and with ラ変{へん} verbs it followed the 連体形{れんたいけい} (adnominal form). (NB: One could think of it as u being part of the morpheme: -ube-.)

Connecting to things after it: べし inflected like an adjective:

未然形 o   べから
連用形 べく  べかり
終止形 べし  o
連体形 べき  べかる
已然形 べけれ o
命令形 o   o

Evolution: べし did not evolve like a normal adjective would (i.e., become べい and end be able to sentences), but instead did something weird, presumably due to its status as a 助動詞 and not a 形容詞.

Now

Currently, べき behaves like this:

Connecting to things before it: べき still behaves completely like a 助動詞 in this sense -- you need a fully surfaced verb to connect it to:

x猫だべき
x猫なべき
x猫のべき
x猫べき
o猫であるべき

x熱いべき
o熱くあるべき

Connecting to things after it: This is the odd bit. べき behaves a lot like 同じ when connecting to things after it: For nominals, べき it connects directly. When concluding sentences, it takes the copula (which can be ∅ in informal speech, but I think most people think of the copula still being there).

やるべきこと
行くべきだ

(Side note: there is also べし still around for ending sentences which people use when trying to sound archaic or pompous or whatever, but amusingly, some people say べしだ which means some people treat it as a noun also.)

Your question

As written in other answers, but now with reasons:

  • You cannot use ないべき, because べき needs to attach to a fully-surfaced verb, and there is none in ない (it is a 助動詞). なくある is not acceptable (because it is the 助動詞「ない」 not the 形容詞「無い」).
  • You can use the old way of negating べき, which is べからず, but of course you will sound archaic if just using it in normal speech, like you're saying a proverb or quoting something.
  • The new way of negating it is by negating the copula: べきでない/べきではない.

However, there is a lingering thing that needs to be discussed:

You should not [eat the cake]. ⇒ You shouldn't eat the cake.
You should [not eat the cake].

In English (at least in my opinion), there is a subtle ambiguity in focus between "You should not eat the cake." One way to read it is that there is an action, and you should not take it. The other way is that there is an action of not doing something, which you should take. The former way can be contracted but the latter cannot.

(If you can't tell the difference, consider the dialogue: "Should I eat the cake, or should I not eat the cake?" "You should not eat the cake.")

This is of course very subtle. What's the situation in Japanese?

In Japanese, you use べきでない for both. Since the negation is all the way on the outside, it sort of suggests the "You should not [eat the cake]." nuance, and if there is a situation that really needs the "You should [not eat the cake]." nuance, you don't have anything like ないべき to use. In the case where I really care about such a nuance, I think I would use ない方がいい.

  • 2
    Regarding evolution, the expected beki > bei certainly does exists and is used by many everyday. kotobank.jp/word/… – Dono Sep 11 '14 at 7:09
  • Yes, I did not mean to suggest otherwise. There is also べ which evolved from べし as well, but has changed syntactic class and meaning quite significantly. – Darius Jahandarie Sep 11 '14 at 16:12
  • What do you mean by "べし used to be a 助動詞 (auxiliary)"? According to dictionaries, it still is a 助動詞. Also, what do you mean by "connecting to things before it" and "connecting to things after it"? To me, both cases look the same, i.e. べき modifies the verb that it attaches to, just like any 助動詞. Or perhaps I'm missing something crucial. – 3 to 5 business days Sep 12 '14 at 5:57
  • (a) Whether べき is still a 助動詞 depends on how you define the syntactic class. I think that the reasonable formula of that class includes it, but there are easily arguments here (e.g., no other 助動詞 takes だ). (b) "Connecting to things before it" and "connecting to things after it" are not cases, they are me attempting to break down the syntax of べし into two parts: how the things before it behave, and how it inflects based on the things after it. – Darius Jahandarie Sep 12 '14 at 6:34
  • b) Oops, my bad. I thought you were talking about two different types of べき; didn't realize you were talking about the same べき. Also, I don't think やるべきこと is weird - べき is after all the 連体形 of べし; whereas 行くべきだ or 行くべきである is the odd one - though I would say べき has a defective/odd 終止形 instead. – 3 to 5 business days Sep 13 '14 at 1:59
6

Most naturally, you can use one of the two below.

「[遊]{あそ}ぶべきでない。」

「遊ぶべきではない。」

The second one places more emphasis on the negation.

  • That just sounded so weird to me, I lazily did not even check with a native speaker. I sense that many English native speakers often misuse "べき" (myself included) because it is such a quick and easy translation of "should". I'll study this more. thank you. – user312440 Sep 11 '14 at 12:42
2

There is a word that is not used so frequently in everyday speech but that nonetheless performs this task: べからず. You use it in the same was as べき/べし. An example on alc shows the following sentence:

自然を侮るべからず。
Don't underestimate nature.

I am not a native of course, so I can't comment on precisely where you should and shouldn't use it, but I'd say in most situations, unless you know it's OK to use it, you should just opt for the simpler ~べきではない or ~しないこと or ~してはいけない or something similar (aka see 非回答者's post). In general searching I see it also used in the phrase 「べからず集」 to refer collectively to things you should not do (like as a list).

  • 1
    What is 「~ないべき」? – l'électeur Sep 11 '14 at 4:09
  • How about 「~べきじゃない」? – Sjiveru Sep 11 '14 at 4:16
  • @非回答者 I blindly copied from the original post, my apologies. – ssb Sep 11 '14 at 4:37
  • I learnt that 〜べからざる is used in notices such as 「芝生に入るべからず」, "keep of the grass" in the park, although I can recall seeing it (〜立ち入り禁止 seems to be more common). – Tim Sep 11 '14 at 12:21
  • @Tim that is certainly how the Makino grammar dictionary treats it. I've never personally seen it in use anywhere, though, so I didn't include it. Maybe it should be in there... – ssb Sep 11 '14 at 12:26

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