Page 172 - Makino,Tsutusi.DictionaryOfIntermediateJGrammar

1. Vmasu kaneru (GI: 2) is often used in formal spoken or written Japan
Qe
to express politely that the speaker 1 writer cannot do s.t. owing to
Olne
circumstance, as shown in KS(A) and Exs. (a) - (d).
2. The negative version, i.e., Vmasu kanenai is actually a double negati,
e,
so it literally means 'can do st.,' but it actually means 'it is very possi,
ble' or 'might.'
3. The verb that can take -kaneru is a verb that takes a first person human
subject. So verbs such as kowareru 'break,' am 'exist,' kawaku 'dry up;
harem 'clear up,' kumoru 'become cloudy,' etc., cannot take -kanem. r,
contrast, the verb that can take -kanenai can take either the third person
human subject (as in Exs.(h) and (i)) or the third person non-human sub.
ject (as in Exs.(j) and (k)).
4. None of the regular potential forms can take -kaneru either, because it
creates double potential meaning.

However, there are two exceptions: wakaru 'can figure out' and dekiru
'can' (used with a Sino-Japanese compound) can take -kaneru, as shown
in KS(A) and Ex.@), respectively.
5. Ex.(g) is an idiomatic case which comes from Vmasu of machi-kanem
'cannot wait' and is exceptional in that it takes a third person subject
unlike other cases of the Vmasu kaneru. No other new combination like
o-machi-kane is possible.
6. As explained in Note 3, -kaneru takes the first person, but when the