What are controversies? I guess there is a controversy whenever there is more than one point of view. So, for example, I might think that the Village People were one of the musical giants of the twentieth century, but you might not agree. We have a controversy. If we take this approach into psychology then we will find that everything is controversial, because for every piece of evidence that is put forward, there are a number of interpretations of that evidence. Psychology, and all other sciences, develop through debate and controversy. It is a part of how they operate. In the context of this book, however, the term controversy has a special meaning.