Theoretically, the fundamental problem with the presumed consent argument is that it cannot explain why there is always some degree of uncertainty about the occupational risks of working in the medical profession, particularly stemming from new and emerging diseases. Quite simply, if there was little or no knowledge of a risk at the time the individual became informed and gave their (tacit) consent, then this individual never accepted the risk, implicitly or otherwise, because it was unknown at the time the individual was informed. From a historical perspective, it is possible to see that while the medical profession was once concerned only with treating diseases, its vocational responsibility came in time to include preventative, promotive and rehabilitative healthcare services. As the notions of human rights and patient rights have developed and become widespread, perceptions about the health profession have changed at the community level. Diseases that once killed millions of people can now be treated with a simple medicament, but today we are faced with new and challenging diseases unheard of in the past. As a result, the continuous cycle of changespurred on by greater knowledge and technological advances and confrontations with new and untreatable diseases -serves to alter the identity and nature of the medical profession, and out of all this arises a constant degree of uncertainty. This characteristic uncertainty is present both when the individual chooses the profession and throughout their education and training periodand, indeed, for the entirety of their professional career. It is therefore not possible for someone to be fully informed when they choose their profession, nor is it possible for them to become fully informed during their education and training; nevertheless, the person should be informed about the uncertainty involved with working in the medical profession. In the light of this uncertainty, answers such as "if I had known I would not have chosen it" are not very meaningful, because there is no way to anticipate all the potential risks one might encounter in the course of a professional life. The only sure thing amid the uncertainty is that diseases such as SARS and avian 'flu will always continue to emerge.