Page 424 - Practical English Usage 3ed - Michael Swan, Oxford

passives (8): he was considered a genius 419
4 preparatory there
With some verbs (e.g. say, think, feel, report, presume, understand), the passive structure is possible with there as a 'preparatory subject'.
There are thought to be more than 3,000 different languages in the world. (= It is thought that there are ...)
There was said to be disagreement between Ministers.
5 perfect, progressive and passive infinitives
A passive verb can be followed by a perfect, progressive or passive infinitive.
He is believed to have crossed the frontier last night.
I was told to be waiting outside the station at 6 o'clock.
The hostages are expected to be released today.
6 exceptions: wanting and liking
Verbs that refer to wanting, liking and similar ideas cannot usually be used in passive structures with following infinitives.
Everybody wanted Doris to be the manager. (BUT NOT DtJris ltHtS wanted tB be efle Ifttlnttge'.)
We liloo our staff to say what they think. (BUT NOT 01;1;,. staJfare liked t8 say what they think.)
419 passives (8): he was considered a genius
After some verbs the direct object can be followed by an 'object complement'- a noun or adjective which describes or classifies the object.
Queen Victoria considered him a genius. They elected Mrs Sanderson President. We all regarded KJJthy as an expert. Most people saw him as a sort ofclown. The other children called her stupid. You've made the house beautifuL
In passive clauses these are subject complements; they come after the verb.
He was considered a genius by Queen VICtOria. Mrs Sanderson was elected President.
Kathy was regarded as an expert.
He was seen as a sort ofclown.
She was called stupid by the other children. The house has been made beautifuL
For more about object complements, see 607.
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