So an impossible thought came to my mind. I'd like to know if there's any way to have an "is" in a passive tense. It's probably just a result of broken translation, but I'll try to lead you to it.
- A service "is provided" – a straight-forward passive, where the verb is in past participle
- Something "is existing" – valid language (verb in present participle), although it would be better said simply "exists"
- Something "is existed" – a grammatically correct passive (past participle), right? right?
- Something "is been" – a grammatically correct "is" passive
Now I have no idea what this would mean, because the English "is" is quite different from the Finnish equivalent which is also used to express "exists" and "has". But I could imagine it being used to convey something like "we are being", to use the "we" passive.
Still, is this valid English? I recognise this has no practical purpose, but it didn't stop me from wondering about this for hours. Languages are fun!
Sources discussing this topic in other ways: SX, Quora, although neither of them mention it being a passive.
Best Answer
'Be' is an overworked word. Relevant usages here are:
He is the tallest lad in the class. He is very tall.
2a. Be is an auxiliary/auxiliary verb, used with present participles to make 'continuous' constructions such as
He is eating his tea. He is/was/will [then] be sleeping.
But as you say, ' ... is existing ...' sounds far from natural. Stative verbs often resist the formation of continuous forms. *He is possessing a new car. / *He is being cold. / He is being rude.
In the sentence 'Albuquerque is located in New Mexico', 'located' exemplifies the 'adjectival passive' according to H & P, but in the sentence ‘The source of the White Nile was located in 1937 [by the German explorer Burkhart Waldecker]', 'was located' is the 'be-passive'. The difference is that the be-passive has a covert – or, if the by-phrase is included, overt – agent (here, Herr Waldecker).
Note that some sentences are ambiguous. 'The window was broken' may be either passive construction. 'The window was broken, we noticed as soon as we arrived' must be the adjectival passive, and 'The window was broken by the hailstones' must be the be-passive. Also, there is arguably a continuum between verbiness and adjectiveness in sentences such as 'He is loved'.
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Not all verbs, and no intransitive verbs (or rather intransitive usages), passivise. Exist is intransitive and be has rare excursions as an intransitive verb ('I am') (I'll not over-complicate by listing this as number (4) in the list here) which your fourth example seems to be searching for. Copular forms don't passivise either, though they may invert: 'Our Johnny is a fine boy.' ↔ 'A fine boy is our Johnny.'
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2b. To complicate matters, there is a rare usage of be to form the perfect construction, where have would be by far the most normal auxiliary of choice. The be-perfect is archaic or nowadays a literary style choice, except in the odd expression ('He'll let us know when he is/has finished').