Why is 高いです acceptable but 高いではあります not acceptable?

Question

This interesting thread got me thinking about the various forms of the copula and how です is a contraction of で（は）あります. I am wondering why the standard X は Y で（は）あります does not seem to work for certain words, like i-adjectives. Please correct me if I am wrong, but I think that the following examples show what I mean:

(1) これは高いです。　O

(2) これは高いではあります。 X　

(3) 彼は元気です。 O

(4) 彼は元気ではあります。O

(2) is the only one that feels unnatural to me but I'm not sure why.

Answer 1

This is because an i-adjective does not require だ (or its te-form で) in the first place. です at the end of a sentence like これは高いです is not a copula but a politeness marker which never conjugates.

• Why should I use つかれました and not つかれたです:

  Usually, です is a polite copula, similar to だ but more polite. But です can also be a politeness marker added to adjectives. When it's a politeness marker, です doesn't inflect for tense.

• です after some verbs

  In Japanese, there's no need for a verb like be to show tense on adjectives. Adjectives can indicate tense all on their own, using the endings -い and -かった. In this case, です doesn't have its usual grammatical function. Instead, it's functioning as a politeness marker.

Instead, you can say これは高くはあります without using だ/で at all.

Answer 2

Addendum: derivations and grammar

Adding onto naruto's answer.

One additional way of looking at this that might help explain why で[は]あります cannot be used with ～い adjectives, is that で (not だ nor です) evolved from earlier にて. This is a hint -- the に is essentially the same as the adverbial に added to な adjectives. Examples:

• 元気な [NOUN]
• 元気に [VERB]
• 元気だ (where the だ is the copula "is")
• 元気です (where the です serves as both the copula "is", and as a politeness marker)
• 元気‍である → older form 元気‍にて‍ある

The corresponding grammatical structures for an ～い adjective:

• 高い [NOUN]
• 高く [VERB]
• 高い (where the ～い adjective all on its own already forms a complete predicate -- we don't need a copula. Saying 高い‍だ is a bit like saying "it is is tall".)
• 高いです (where the です serves just as a politeness marker)
• 高‍く‍ある
  The く here aligns with the に particle in the older form にてある for ～な adjectives.

To modify ある, both ～い and ～な adjectives must be in the adverbial form, although this is obscured by the contraction にて → で.

(As for why ～な adjectives also require the connecting auxiliary ～て before ある, whereas ～い adjectives do not [*高く‍て‍ある is incorrect], I haven't found any cogent explanation, so if anyone can add that, I'd be most grateful.)