After more than 25 years of studying the holocaust, I seemed to be going round and round in circles. The question why ? always seemed to recur. Robert Wistrich provides a well written and researched survey of this period which brings out all the main themes and historical explanations. Why did the holocaust happen ? Robert Wistrich provides a lucid but partial answer. The explanation is that there were substantial numbers of deviant people living in the morally bankrupt societies of 30s & 40s Germany and Austria. The Nazi horror was possible because an evil philosophy found so many willing recruits and passive hangers-on. German and Austrian society was rotten even before Hitler came to power. Thankfully, we have learnt from this.