Phrases Made w/ the Bases of ～べきだ: ～べくもない, ～べからず・ざる, ～べく, ～べくして, & ～べし
Back in our first lesson on ～べきだ, we learned how it is an auxiliary verb pertaining to “obligation” but that its scope of use has been diminished substantially in Modern Japanese. Nonetheless, the auxiliary still holds on, with most of its bases still functional despite having become archaic.
In this lesson, we will go over various advanced grammar points which are derived from its other bases, and in doing so, we will view these other bases as being derived from ～べきだ’s predecessor ～べし.
The Extant Bases of ～べし
The auxiliary “verb/adjective” ～べきだ is etymologically1 better viewed as an “auxiliary adjective,” as it is merely slightly corrupted by the addition of the copula verb to its 連体形. While this did give rise to its new, modern 終止形 of ～べきだ, it also rendered certain other bases obsolete, notably its /-kari/ 連用形 and its 已然形, whose functionalities have been taken over by the copula built into ～べきだ.
Nonetheless, this lesson will be more so an introduction to ～べし as it pertains to Modern Japanese than it is a second installment of ～べきだ. As such, without further ado, the bases of ～べし are as follows:
| 未然形 | 連用形 | 終止形 | 連体形 | 已然形 | 命令形 |
| べから- | べく- （べかり-） | べし | べき-・ （べかる-） | （べけれ- ） | 〇 |
Orthography Note: ～べし can rarely be seen written in kanji as 可し.
While the modern ～べきだ heavily emphasizes duty and what is deemed appropriate, in the past, these usages all stimmed for an overarching notion of latent potential as well as natural course of events, with agency or the lack thereof among other factors dictating the exact nuance of the auxiliary. The loss of nuances attached to latent potential (潜勢), nuances which we will soon touch upon in their individual environments, is likely attributed to the inclusion of the declarative copula だ into the structure.
～べからず・べからざる
The 未然形 of ～べし, べから-, is heavily used in Modern Japanese with the classical negative auxiliary verb ～ず in the context of to-the-point negative imperatives. While not so common in the spoken language, this pattern is great for signage. Think “DO NOT TOUCH” or “KEEP OFF THE GRASS” as perfect environments for this grammar to be employed.
1. 触るべからず！
DO NOT TOUCH!
2. 芝に入るべからず！
KEEP OFF THE GRASS!
3. この橋、渡るべからず
DO NOT CROSS THIS BRIDGE!
4. 関係者以外、敷地内に入るべからず
NO UNAUTHORIZED PERSONS ARE ALLOWED TO ENTER THE PREMISES
5. 働かざる者は食うべからず
Those who do not work shall not eat
The auxiliary ～べし largely revolves around the notion of obligation, which is also anchored in place by the notion of “latent potential.” The things that ought to be the case are the things that one naturally can and should do. As it pertains to negative structures, we see that while still quite archaic, ～べからず can still be used to mean ～することができない, with a heavy emphasis on it naturally being the case that the agent cannot perform X. Moreover, this lack of “latent potential” is more likely to be seen as ～べからざる with X directly modifying a nominal phrase. Note that ざる‐ is simply the 連体形 of the auxiliary ～ず.
6. 予測すべからざる事態
A situation that one cannot predict
7. 許すべからざる罪
An unforgivable sin/crime
8. 現代社会では、スマホやインターネットなどは欠くべからざる存在となっている。
In the modern age, things such as smartphones and the Internet have become indispensable things (in our lives).
9. 遼平君は、我がチームには、欠くべからざる一員である。
Ryohei-kun is an integral member of our team.
10. 羽なければ空をも飛ぶべからず。
If one has no wings, one cannot fly through the skies.
Another pattern utilizing ～べからず worth noting is ～ざるべからず, which is akin to the modern ～なければならない to indicate obligation via a double negative construction. Of the two, ～ざるべからず places even heavier emphasis on the duty bore by the agent.
11. 天皇を重んぜざるべからず。
One must honor the emperor.
～べくもない
～べくもない is a combination of the /ku/-type 連用形 of ～べし followed by the adverbial particle も and the negative auxiliary ～ない. Together, the structure translates to “there is no way/it is possible” even if there is intention to make it happen. While we view the modern ～べきだ as pertaining solely to “obligation,” several other usages existed for its predecessor ～べし which have since fallen out of use. Of these, the indication of “potential,” albeit always with negative forms, was one of those now obsolete meanings. Granted, this sense of “potential” does derive from the underlining meaning of “obligation/strong resolve/appropriateness,” with negation facilitating the inability for said impetus to be set in motion.
12. 将来、東京大学の教授になろうなんて望むべくもない。
There’s no way that I could ever become something like a Tokyo University professor in the future.
13. そう聞いても、ザイダさんには想像するべくもない光景だった。
Though Zaida-san was hearing about it, the scene was one that she couldn’t have ever imagined.
14. セスは遼平を死ぬほど愛している、これは疑うべくもない。
Seth loves Ryohei to death; there is no doubt about that.
The closest structure to ～べくもない would be ～できるはずがない, which focuses on there being no means, whereas with ～べくもない, the focus would be on there being no chance of that resolve or circumstance ever coming to pass in a very emotionally charged fashion. One other major difference, however, is that ～べくもない can also be paired with non-volitional verbs to indicate the zero chance of something ever occurring.
15. 季節の推移はやむべくもない。
The changing of the seasons is inevitable.
～べく
The /ku/-type 連用形 of ～べし, ～べく attaches to verbs of volition, which serves as the initiative that the speaker feels determined/obligated to pursuit, with the predicate Y that follows being the means. As such, ～べく is quite similar to ～ために but with added emphasis on duty.
16. 早く帰るべく、準備をし始めた。
I’ve become to make preparations so that I may get home early.
17. 我々は、将来を担うべく努力することを誓います。
We vow to endeavor to bear the future.
18. 国民を守るべく、研鑽を欠かさない。
(He) never falls short of improving (himself) so that (he) may protect (his) citizenry.
19. 作文嫌いを克服すべく、毎日、セス先生が掲げてきた「The Document Challenge」に挑むことにしています。
So that I may overcome my dislike of writing, I have decided to take on “The Document Challenge” which Seth-sensei has touted up to this point.
20. 筆者は最近、社長になるべく日夜努力を重ねている。
I (the person writing to you) have been recently working day and night to become a company president.
One set phrase which utilizes ～べく that is of considerable importance in formal settings, is the word しかるべく which roughly translates to “as one sees fit.” It combines しかり―a contraction of しかあり meaning “absolutely the case”―and ～べく.
21. しかるべく対応いたします。
I shall handle the matter as is appropriate.
～べくして
Utilizing the conjunctive particle して, ～べくして is most often used to indicate the necessity behind something that is predicted by the speaker to happen having happened. Incidentally, in this construction, the verb that precedes ～べくして will also be the same verb that follows it, leading to a translation for ～べくして of “it’s only natural that.” This meaning of a “natural course of events” is inherently tied to the latent potential hinted at in other structures (like in ～べくもない in the negative).
While this structure is largely used with intransitive verbs, the commonality behind all examples of this pattern does not lie in transitivity but rather in how “volition” does not play a part in the action occurring.
22. これは勝つべくして勝った試合です。
As for what you see here, this match was one that we were naturally going to win.
23. チャンスを掴める人は、掴むべくして掴んでいる。
Those who snag chances are those who naturally grab them (as they come along).
24. 起こるべくして起こった出来事だ。
What occurred is what would have naturally taken place.
25. 負けるべくして負けた。
It’s only natural that (we) lost.
Though not nearly as common and not touched on at all in the JLPT N1, ～べくして does have a rarely seen 逆接 nuance of “even if one can do X, (outcome Y is unfeasible).” This can also be adapted in a way so that the verb standing in as Y is marked by a negative form of ～べし to capitalize on this unfeasibility, which in the case of Ex. is to indicate a negative command of the vein of “should not.”
26. その教科書を読むべくして理解しがたい。
Even if you can read the textbook, it is difficult to understand.
27. この説は言うべくして行うべからず。
Even if you can say the theory, you shouldn’t carry it out.
～べし
Though clearly archaic, from the sense of obligation, the 終止形 ～べし may also indicate a forceful command related to duty. It is the affirmative rendition of ～べからず mentioned earlier.
28. 辞職すべし。
You should resign!
29. 培った力を存分に発揮すべし！
You must make full use of the strength/skills you’ve nurtured!
～ざるべし
When ～べし follows the negative auxiliary verb ～ず, ～べし follows its 連体形2, and in this context, ～べし simply denotes the meaning of “absolute certainty” that the predicates is NOT the case, as it is being paired with the negative.
30. この人々の深き志は、この海にも劣らざるべし。
The deep kindness of those here surely outmatches that of this sea (in its depth).
From the 『土佐日記』.