particle に - Causative Form - Difference between 子供に本を読ませる and 子供を本を読ませる

What is the difference between these two examples?

1. 子供に本を読ませる


2. 子供を本を読ませる

Please give me some other example to illustrate the difference.

Answer

子供を本を読ませる is ungrammatical, and you have to say 子供に本を読ませる.

Here are the basic rules for causation:

1. For verbs which take を, the agent (or "causee") is marked with に. Such verbs are usually transitive verbs, but some intransitive verbs take を, too.


2. For verbs which don't take を (i.e., most intransitive verbs), the agent is marked with を.

In your question, 読む is a fairly simple transitive verb which takes an object marked with を. So the agent (子供) must be marked with に.

Other examples:

• 子供を眠らせた。 I made the kid sleep.
  (眠る is a simple intransitive verb which never takes an object)


• 子供に歯を磨かせた。 I made the kid brush his teeth.
  (磨く is a simple transitive verb)



• 子供に磨かせた。 I made the kid brush (it).
  (The object is omitted, but still the agent is marked with に because 磨く is transitive. 子供を磨かせた would mean "I made (someone) brush the kid")


• 子供を家に帰らせた。 I made the kid return home.
  (帰る is an intransitive verb which takes に, but never takes an object marked with を)


• 子供に道路を渡らせた。 I made the kid cross the road.
  (渡る is an intransitive verb which does take を)

And you can find some edge cases in this question.