Lucius and the diary

[Hagrid]

No: HPFGUIDX 178887

> TKJ:
> > do we know WHY exactly Lucious thought it was a good idea to 
> > give the notebook to Ginny? 
> 
> Magpie:
> Lucius didn't know it was a Horcrux, but he did seem to know that 
> the Diary would unlock the Chamber of Secrets using another student. 
> So the idea was to discredit Arthur and fight back against his raids 
> etc. by having his own daughter purge the school of Muggle-borns.

aussie:
Dumbledore told Harry 3 reasons in HBP chap 23 ...
- discredit Arthur (who was conducting the raids) by giving it to 
Ginny 
- get Dumbledore kicked out of the school
- get rid of a Dark Object that could incriminate the Malfoys

Lucius didn't know it was a Horcrux, but knew it would help open the 
Chamber of Secrets again.
aussie