The natural state of the human body is that of good health. Yet it would appear to be rather difficult to maintain the body in the state of good health throughout a person’s entire lifetime. Although illness may seem to be a common human experience, it can manifest in a variety of different forms and to varying degrees of severity; the common cold, for example, is self-limiting and short-lived, whereas many chronic conditions, such as rheumatoid arthritis, are considered to be incurable and lifelong. It may be assumed from this that illness is largely unavoidable or is even an inevitable aspect of human life; but this would be a mistaken assumption, as this book will demonstrate. Nevertheless, the fact that large numbers of people experience some form of illness during their lives raises some fundamental questions, not least of which is: why does it occur? In other words, what really makes people ill? The usual responses to such questions refer to two interrelated ideas, both of which are widely believed to be fundamental truths. The first of these ideas is that illness occurs because a person has contracted a disease of some description. The second is that each disease is a distinct entity that can be identified by the unique symptoms it produces within the body. This book will also demonstrate that these ideas are not truths. The conventional approach to illness adopted by virtually all systems of ‘healthcare’ is one that employs remedies, or ‘medicines’, that are claimed to alleviate or bring an end to a patient’s symptoms. This approach is based on the idea that the cessation of symptoms indicates that the disease has been defeated and that this successful outcome has been accomplished solely by the ‘medicine’.