Here, we come up against the perennial conflict between psychiatric and legal understanding of what constitutes an obsession. While Fritzl claims he had an "irresistible impulse" which he could not conquer, lawyers will argue that he had an "impulse not resisted" – in other words that his freedom of choice and decision was always intact.

Therein lies the basis of most moral understandings in most religions, which all, in some way or other, insist upon Free Will. Fritzl is a perfect example of this, spending years preparing the dungeon for his daughter's abduction.

There is nothing impulsive about a three-year building plan. Of course the question of his sanity is bound to arise. All this premeditation demonstrates he knew what he was doing; he also knew what he was doing was wrong, for he has said so.

But it is possible to undertake sane steps towards a completely insane end; the madness lies in the intention, not in the method.