Helfen in passive

Question

I have read in many German Grammar books that intransitive verbs cannot be used in the passive. But it seems this is not the case.

For instance. "Helfen" is an intransitive verb. Yet the following passive sentence is acceptable to all of the German speakers I have asked:

Ihm wird geholfen.

What am I missing here?

Answer 1

The simplest definition of how to build a German passive I can come up with is

1. The accusative object of the sentence in active transforms into the subject of the sentence in passive
2. The subject of the active sentence can transform into the new sentence by adding it with "von" + dative or "durch" + accusative
3. The predicate of the active sentence is transformed into the passive sentence's predicate.
4. Dative and prepositional objects stay as they were

(1) will not work for "helfen", as "helfen" (or other intransitive verbs) do not carry accusative, but rather dative objects, so such a sentence wouldn't have a subject.

You can work around this by adding an impersonate subject to the sentence ("Es") and form a sentence like

Es wird ihm geholfen

and your example is simply an abbreviation of the above - "Es" can be omitted if it is replaced by another sentence component taking position 1 (here the dative object).

What you are seeing there is called unpersönliches Passiv. And your grammar books should mention this as an exception to their "can't form a passive".