べきだ

Auxiliary (Intermediate ㊥ 11)

An auxiliary which expresses the speaker's judgment that someone/something should do something or should be in some state.

Equivalent: Should; ought to

この論文は書き直すべきだ。: This thesis should be rewritten.
そんなことを人に言うべき{では/じゃ}ありません。: You shouldn't say that kind of thing to people.
君も来るべきでしたよ。: You should have come, too.
山田には話すべき{では/じゃ}なかった。: I shouldn't have told that to Yamada.
話すべきことは全部話しました。: I told you everything I should tell you.
自分のことは自分です（る）べきだ。: You should look after yourself. (literally: You should do your own business by yourself.)
今、家を買うべきじゃないよ。: You shouldn't buy a house now.
それは課長にも言っておくべきだったね。: We should have told that to our boss, too, shouldn't we?
彼は結婚なんかす（る）べきじゃなかったんだ。: He shouldn't have married.
我々はもっと創造的であるべきだ。: We should be more creative.
この状態が現実であるべきだ。: This state should be the reality.
調査の結果、驚くべきことが分かった。: As a result of the investigation, a surprising thing (literally: something one should be surprised at) was discovered.
田中は全く軽蔑すべき男だ。: Tanaka is indeed a despicable man (literally: a man whom one should despise).
あるべき所に記述がない。: There's no description where there should be one.

Formation

(i) Vinformal nonpast	べきだ
	行くべきだ	Should go
Exception	する→{す/する} べきだ	Should do
(ii) {Adjective な stem/Noun}	であるべきだ
	積極的であるべきだ	Someone should be positive
	目的であるべきだ	Something should be an objective

Notes

1. Tense and negation are expressed by conjugating べきだ. [See Key Sentences (A) - (D) and Examples (a) - (d).]

2. The prenominal form of べきだ (i.e., the form which modifies a noun) is べき. [See Key Sentence (E) and Examples (g) - (i).]

3. べきだ usually expresses the idea that someone/something should do something or be in some state because it is his/her responsibility or duty, because it is the right thing or a good thing to do, or because it is the right state or a good state to be in. [See Key Sentence (A) - (E), Examples (a) - (f) and (i).]

4. べきだ also expresses the idea that someone is expected to do s.t. [See Examples (g) and (h).]

5. Adjective い stem+くあるべきだ, as in (1), is a possible form but this form is not commonly used.

体は年をとっても心は若くあるべきだ。
Even if one's body gets old, one's mind should be young.

6. べきだ is not used when the speaker is younger than the hearer or lower than the hearer in status. For example, (2) is not appropriate in the given situation.

??先生、それはお忘れになるべきです。
Professor, you should forget it.

【Related Expressions】

I. ものだ also expresses the idea that one should do something as one's duty, as in [1].

[1]

学生は勉強するものだ。
Students should study.

However, ものだ is used only in a generic statement to express a social norm. Thus, in a specific situation, as in [2], it cannot be used.

[2]

君は勉強する{べき/*もの}だ。
You should study.

(⇨ もの(だ)㊦)

II. In terms of forcefulness, べきだ is weaker than なければならない and stronger than たほうがいい, as in [3].

[3]

a.	君はもっと勉強しなければならな。	stronger
	You must study harder	↑
b.	君はもっと勉強すべきだ。	\|
	You should study harder.	\|
c.	君はもっと勉強した方がいい。	↓
	You'd better study harder.	weaker

(⇨ なければならない㊦; ほうがいい㊦

III. はず also expresses the idea of "should." However, はず is used when the speaker's expectation is involved. Compare the following sentences.

[4]

a. このレポートは山田さんが書き直すはずだ。
Yamada should rewrite this report. (= I expect that Yamada will rewrite this report.)
b. このレポートは山田さんが書き直すべきだ。
Yamada should rewrite this report. (= Rewriting this report is Yamada's duty.)

[5]

a. この本はここの図書館にあるはずだ。
This book should be in this library. (= I expect that this book is in this library.)
b. この本はここの図書館にあるべきだ。
This book should be in this library. (= Housing this book is this library's responsibility.)

(⇨ はず㊦)