I know two such people. One has in fact affected my career and life, in turning me off a job I loved for 23 years and somehow providing the circumstances that resulted in my starting to write songs.

If he was your neighbour, you'd love him - congenial, friendly, always willing to help, bright and friendly.

At work he commits heinous crimes that - I am sure - would horrify him if you told him so at home.

I am convinced that he cannot help it. Each of his personalities cannot see the other.