A young woman says that intrusive violent thoughts sometimes enter her mind and that she finds them horrifying and wishes they would stop, but she is clear they are her own thoughts, arising from her own mind, however unwelcome. Before revealing the answer: is this thought insertion?

No. Despite the intrusive and distressing quality of the thoughts, she recognises them as her own — this is the crucial point of ownership that distinguishes an obsession from thought insertion. Thought insertion requires a conviction that the thought has been placed into the mind by an outside agency and is foreign in origin, not merely unwanted. Here the content is disturbing, but the sense of authorship is intact, which points toward an obsessional thought rather than a passivity phenomenon.