The reader noting the title of this chapter may wonder, after all that has been written on the subjects of Bulimia nervosa (hereafter BN) and Anorexia nervosa (hereafter AN), whether a new theory of these conditions is really needed. It will also not have escaped the reader's notice that this chapter not only offers such a theory, but also promises to take care of both conditions with it. Given all the work that has gone into distinguishing BN and AN from each other as separate eating disorder syndromes, whether or not they occur in the same person, can it be credible that the two have a common basis and may even be the same Janus-faced syndrome? This chapter will try to demonstrate to you that they are in fact results of a common etiology and that to argue this is only common sense. As to whether they are the same syndrome, I fully allow for the branching of symptom choice at different moments in the evolution of eating disorders, even if the root is the same. This enables me to continue to learn from all the literature built around thinking of these conditions as separate syndromes. I will argue that these separate clinical pictures are in fact simply branches of one basic syndrome. But even if this chapter should fail to live up to its billing and prove this to every reader's satisfaction, it can hardly shed less light on the etiology of the conditions than recent efforts to clarify them have done. Polivy and Herman (2002) concluded their review article, ``Causes of Eating Disorders,'' with the statement that, although there are certain factors that may be necessary conditions for the development of these eating disorders and that there are certain risk factors that warrant further study, there is (a) no conclusive proof of what causes BN or AN in any one individual and (b) no understanding of the mechanism underlying these eating disorders. In ``Risk Factors for Eating
Disorders,'' Striegel-Moore and Bulik (2007: 183) wrote, ``the state of knowledge concerning the risk and causal factors of eating disorders is frustratingly incomplete.'' They also expressed concern about the neglect of the eating disorder ®eld both by the US Centers for Disease Control and by the World Health Organization:
We attribute much of this marginalization to pervasive misperception about the volitional [emphasis added] nature of eating disorders, which has impacted research; third-party reimbursement; and most tragically, families and sufferers who have known all along that eating disorders are far more grave than merely a choice to pursue thinness.