12.9 Summary 245 it is right to release nanoparticles into the environment when the effects of inhaling those nanoparticles are imperfectly understood. Clearly that is wrong if (for example) one's choice of ethics is based on Hippocrates' dictum, "Primum, nil nocere." Most of these books seem, however, to overlook the fact that the choice of ethics is ultimately arbitrary. As Herbert Dingle has sagely pointed out, there exists no final sanction for any particular answer to the question, "How shall I choose what to do?" It follows that books dealing with ethics can be of two types: one type can present a system (possibly with the intention of convincing others that it is worthwhile adopt- ing it). The second type starts with a particular choice of ethical system and examines the consequences for action in a particular area (e.g., nanotechnology). It seems that most of the books dealing with nanoethics are of the second type, but the defect of omitting to clearly state what are the ethics on which they are based seems to be widespread. Perhaps there is an underlying current of thought that the new era of rationality which might be ushered in by nanotechnology and its way of looking at the uni- verse would lead to an indefeasible and unique set of "natural" ethical principles. Certainly the technology encourages a more consequential attitude: if one knows a structure with atomic precision then its properties should be more predictable than