Suppositional ～（よ）う w/ Adjectives & Verbs
In this lesson, we will learn about how the suppositional auxiliary ～（よ）う works with adjectival and verbal predicates, putting aside how this grammar has largely been replaced by 終止形＋～だろう・でしょう. Because this grammar may still be found in older literature, set phrases, and in niche grammatical environments, the examples showcased are predicated on their being antiquated.
Adjective: ～う
The suppositional auxiliary ～う attaches to the 未然形 of adjectives, which conjugates as follows.
| Class | 未然形 | ＋～う |
| 形容詞 | karo– | 新しかろう 寂しかろう 早かろう |
These forms are identical to using 終止形＋だろう. Unlike だろう, which has its polite speech variant でしょう, this traditional grammar has no plain-polite speech distinction, which is due to the resultant suppositional phrases not necessarily being directed at any given person.
As far as tense/aspect is concerned, adjectival suppositional statements may be interpreted as either being present or future tense. “Would be…” is also often an appropriate translation if the suppositional statement is purely hypothetical.
1. 安かろう悪かろう。(Set Phrase)
You get what you pay for.
2. 早かろう悪かろう。 (Set Phrase)
Finishing early surely pays off poorly.
3. 一人きりは寂しかろう。
It must be lonely being all alone.
4. さぞ楽しかろう。
It must surely be fun.
5. 水面の下を泳ぐ魚たちは悲しかろう。
The fish swimming beneath the water’s surface are surely sad.
6. それを考えるとここはやはり穏便に済ませておいた方がよろしかろう。
Considering that, it would probably be best to settle this without fuss.
～なかろう
With the auxiliary verb ～ない exhibiting adjectival bases, it too may take the suppositional auxiliary ～う, creating ～なかろう which functions as ～ない｛だろう・でしょう｝ for verbs as well.
7. 猪を目の前で解体されては食べる気がしなかろうと思うが・・・
While I wouldn’t imagine anyone would feel like eating witnessing a boar being butchered right in from of them…
From 『道具が語る生活史』by 小泉和子.
The same also goes for the appear of the auxiliary verb ～ない with the copula for nominal and adjectival noun predicates.
8. 純粋な月影石でなかろう。
It is probably not a genuine moon rock.
9. テロでなかろうがデモは規制する。
Though it may not be terror, we will control demonstrations.
Infamous poor words of 石破茂.
～たろう・～ましたろう
The direct predecessors to ～ただろう is ～たろう, which is the case for all predicate types. In the same vein, the predecessor of ～たでしょう for verbal predicates is ～ましたろう.
10. 新しくなかったろう。
It was likely not new.
11. よろしかったろう。
It was surely fine.
12. もう少し注意したなら、成功したろうに。
If you would have paid just a little more attention, you would have succeeded.
13. したら、反対したろう。
If so, I would have been in opposition of it.
14. 散歩の楽しみを覚えたのはいつの頃だったろうか。
When exactly did I first learn the joy of going on walks?
15. ああ、なるほど。あなたはどうも覚えがいい。あれはもう去年のことでしたろう。
Ah, I see. You have a great memory. That must have been last year.
From 『半七捕物帳』by 岡本綺堂.
16. 特に本宅の裏の寮に寝泊りしている若いものは七、八人もいましたろうか、本宅と寮の掃除をするのがそら大変で…。
In particular, with there being perhaps seven-eight young people living in the dormitory behind the main house, cleaning the main house and dormitory was a real pain…
From『語り継ぐなにわ商法』by 和田亮介.
17. 村じゅうの元気な者が森へ逃げこみましたろうが！
Agh, all the well-bodied people of the village have fled to the forest!
From『万延元年のフットボール』by 大江健三郎.
Verbs ＋ Suppositional ～（よ）う
A meaning that has fallen out of use but is still seen in old-fashioned speech and literature is the ability to show supposition (likelihood). This has largely been replaced with ～だろう. Though this meaning is largely defunct, it can be distinguished from the others by not just differences in tone but also by context. This meaning of the volitional endings involves statements about state, not an action in which the speaker has control over.
18a. 長時間歩いたのでお腹もすいていよう。
18b. 長時間歩いたのでお腹もすいているだろう。
You’re also probably starving because you’ve been walking for so long.
19a. 彼らは指摘できよう。(Old-fashioned)
19b. 彼らは指摘できるのだろう。
They’ll probably be able to point it out.
There are some grammatical instances where this meaning of the volitional endings lives on in modern language use. These instances include the patterns ～（よ）うはずがない and （よ）うものなら.
20. そんなことがあろうはずがない。
Such a thing should not happen.
21. 黙っていようものなら、自滅するぞ。
If you are to remain quiet, you will end yourself.
22. そんなものが楽しかろうはずはないのである。
There is no way something like that could be fun.
Another usage of these endings is making rhetorical questions when followed by the rhetorical question-marker か. In this situation, か has a sharp drop in pitch. This usage has largely been replaced by ～（の）だろうか.
23. 許されようか。
Will [I/you/he/she/it] really be forgiven?
24. あやつにはそれができようか。
Can he really do that?
A meaning that has fallen out of use but is still seen in old-fashioned speech and literature is the ability to show supposition (likelihood). This has largely been replaced with ～だろう. Though this meaning is largely defunct, it can be distinguished from the others by not just differences in tone but also by context. This meaning of the volitional endings involves statements about state, not an action in which the speaker has control over.
25. 長時間歩いたのでお腹もすいていよう。
You’re also probably starving because you’ve been walking for so long.
26. 彼らは指摘できよう。
They’ll probably be able to point it out.
～ましょう
終止形＋でしょう is immediately preceded by ～ましょう for verbal predicates. Up until the late 1980s, such phrasing was still quite common in daily speech. While dated, it remains relatively easier to find examples of ～ましょう used in a suppositional capacity than its plain speech counterpart.
27. 明日は雨が降りましょう。
It will likely rain tomorrow.