寝かす

[Toritoribe]

得る never means "capable or able" but "possible only", doesn't it?

No. ～うる can express ability "to be able to do", as dictionaries I quoted above clearly show.
e.g.
〇彼ならあの石を持ち上げられる。
〇彼ならあの石を持ち上げうる。

～うる only expresses possibility when used with non-volitional verbs. (The meaning is close to ～かもしれない for this usage.) These verbs can't have the potential form ～れる/られる since it expresses ability. You've never seen あれる, unlike あり得る, right?
e.g.
×明日にでも地震は起きれる。
〇明日にでも地震は起きうる。（＝起きるかもしれない)

Can I take it when あり得る simply means "possible" we say ありうる? When it means "possible to have" we say ありえる like the example below?

There is no difference between える and うる in meaning.

得ない reads えない only as far as I can see.

うる is originally from the attributive form of a classical verb う. う is 下二段活用動詞 (shimo-nidan verb), so 未然形 (equivalent to pre-nai from) is え (e.g. えず/えぬ). That's why the negative form is only えない, and うない is ungrammatical.

Incidentally I would like to ask the difference in usage between こと and もの. こと after plain verb nominalize the verb. What about adjectives? Do we have to use もの like the example below?

もの is not a nominalizer but a noun "a physical thing" there. It's also possible to interpret that it's a pronoun for 乗り物 or 地下鉄, but, anyway, こと can't be used there because こと is for abstract things. It has nothing to do with whether an adjective or a verb is used in the modifying clause.
e.g.
〇混雑した地下鉄は、初めて乗る人々にとっては、とても煩わされるものとなり得る。
cf.
×混雑した地下鉄は、初めて乗る人々にとっては、とてもややこしいこととなり得る。
〇混雑した地下鉄に乗るのは、初めて乗る人々にとっては、とてもややこしいこととなり得る。

Can we say ものになり得る instead of ものと

Yes. It's said that となる focuses more on the result of the change and になる is on the process of the change, and となる sounds more classical/formal, but they are interchangeable in most cases.

Does it make sense if I say どんなもの instead in the following sentence?

No. ものが起こる doesn't make sense there. Needless to say, there are cases where ものが起こる makes sense.
e.g.
一度地震が起こると、続けて少し規模の小さなものが起こることが多い。
(もの is a pronoun of 地震 here.)

Is でも stronger than も for the meaning of "even" in there?

Yes.

Lastly, can both こと and もの be used to refer to both physical things and abstract things?

It differs depending on the function of those words or sentence structure.

 

[healer]

No. ～うる can express ability

The potential form of a verb can also express both ability and capability, can't it? I suppose non-volitional verbs are excluded where potential form is inexistent.

～うる only expresses possibility when used with non-volitional verbs.

I suppose you refer to ~える as well and ある and 起きる are some of them as per your examples. This is the first time I encounter this lingistic term. Could you please give me a few volitional verbs as well so that I can appreciate the contrast?

とても煩わされるものとなり得る

とてもややこしいこととなり得る

I'm not sure why もの is possible in the former. Is it because もの is the pronoun of 地下鉄 while こと in the latter is the phenomenon of the process of 乗る?

 

[Toritoribe]

The potential form of a verb can also express both ability and capability, can't it?

Yes, it can.

I suppose you refer to ~える as well and ある and 起きる are some of them as per your examples.

Yes and yes.

This is the first time I encounter this lingistic term.

What term are you referring to by "this linguistic term"?

I'm not sure why もの is possible in the former.

It's the same as your original example. もの is a noun "a physical thing" or a pronoun of 乗り物 or 地下鉄.

こと in the latter is the phenomenon of the process of 乗る?

The subject 混雑した地下鉄に乗るの is an action, i.e., not a physical thing.

 

[healer]

this linguistic term

I was referring to

non-volitional verbs

I apologize that I didn't make myself clear. I was referring to non-volitional verbs and I guessed that ある and 起きる as you mentioned were some of the non-volitional examples. I asked some volitional verbs so that I can appreciate the difference. Must verbs be either volitional or non-volitional?

 

[Toritoribe]

I thought you were referring to "non-volitional verbs", but I needed to confirm since you said "This is the first time I encounter this linguistic term". I repeatedly used the term "non-volitional" in my replies to your posts, so I couldn't believe you said that.

For example, in the following ones;

で v に

私達は娘の誕生日パーティーにキャンディーで一杯のピニャータを用意します。 Should パーティーに above be パーティーで for action verb such as 用意する in this case? If not, why? イギリスのために大胆で新しい役割を打ち立てていくのです。 Should 大胆で be 大胆に being the adverb of the な-adjective? I’m not sure how 大胆で comes about grammatically. 毛で覆われたアライグマ I have learnt that the...

jref.com

いられる

Re: 暑い夏の日は、エアコンのおかげで一日中涼しくいられる。 On a hot summer day,the air conditioner works all day to keep us cool. Is いられるabove the potential form of 居る,the common verb いる,to be,to exist,to stay? Is it common to have いられる go with adjectives instead of する or なる? There is also a seperate headword 居られるin...

jref.com

In the former thread, you used the term "non-volitional" by yourself, so you must understand the concept of "non-volitional". Even if you meant "non-volitional verb" specifically, I wrote "The basic difference between なる and する is non-volitional vs. volitional" in the latter one, so I believe it clearly shows that when a verb is volitional, it's a volitional verb.

Must verbs be either volitional or non-volitional?

There are verbs that can be both depending on the meaning or context like 含む, as I wrote in your another thread.

By the way, needless to say, "the potential form of a verb can express both ability and capability" is not the same as "the potential form of a verb always can express both ability and capability." The same goes with ～うる/える.