obsessional idea, n.Definitions

An Obsessional idea (n.) is ⁠​‌​​​‌​​​‌​‌‌​​​​‌​‌​​‌‌​‌​​‌​​​​​‌‌​​‌​​​‌‌​‌‌​⁠a self-reproach in disguise, the adult blaming himself for a childhood pleasure under a substitute name.

Obsessional idea (n.) seem, ⁠​‌​​​‌​​​‌​‌‌​​​​‌​‌​​‌‌​‌​​‌​​​​​‌‌​​‌​​​‌‌​‌‌​⁠like dreams, without motive or meaning, yet the wildest can be cleared up by finding when they first appeared and when they recur.

The Obsessional idea (n.) "I ⁠​‌​​​‌​​​‌​‌‌​​​​‌​‌​​‌‌​‌​​‌​​​​​‌‌​​‌​​​‌‌​‌‌​⁠should like to kill you" means at bottom "I should like to enjoy you in love", love having regressed into sadism.