What is effectiveness?
Almost all attacks on homeopathy, and other complementary and alternative medicine (CAM), are accompanied by the demand for ‘proof of effectiveness’ based on randomised controlled trials (RCTs). When a substance is tested for its effectiveness in causing harm, results can be easily identified by increases in rates of illness (morbidity) or of death (mortality). The details of what harm is caused are less significant than the fact that the substance produces harm of one sort or another in different people. As a result it is easy to use a test such as the RCT to establish harmful effects.
When it comes to establishing beneficial effects, however, the problem is more complex. Instead of initiating a generalised process of change, the intervention must resolve an existing individualised process of change in particular patients. Thus the NHS Clinical Resource and Audit Group quote a report by the NHS Executive to say that effectiveness is
The extent to which specific clinical interventions, when deployed in the field for a particular patient or population, do what they are intended to do - that is, maintain and improve health and secure the greatest possible health gain from available resources. 
This definition makes it clear that
Clinical effectiveness is dependent on the degree to which a treatment fulfils the prescriber’s intention;
The intention is to “maintain and improve health”;
Cost effectiveness is dependent on balancing the degree of clinical effectiveness against the cost of achieving it.
The problem is that the whole definition depends on there being a further definition of what is meant by ‘health’ and a method of measuring changes in this quality. At the same time it has been pointed out that
A doctor who wishes to make himself unpopular in conversations with colleagues need only ask questions of the following kind: ... What exactly do you mean by health? … 
In practice effectiveness is defined by the degree to which an intervention diminishes or removes particular symptoms in a patient, but this creates problems, in that apparent benefits in one area may be offset by harm in another area, referred to as side effects. Which effects are defined as ‘beneficial’, and which as side effects, depends entirely on what results are being sought.  Furthermore, not only does the balance of ‘beneficial’ effects and side effects vary from individual to individual, but there can be no certainty that what appear to be benefits in the short term are not themselves also harmful in the longer term.
As a result orthodox medicine involves a continual process of experimenting to find treatments in which the benefits outweigh the harm, and of reassessing such treatments as a result of their use in clinical practice. This approach has come to be called evidence based medicine (EBM). Neither experiment nor clinical practice, however, is capable of identifying benefit with any certainty, or of eliminating side effects. In other words, each intervention is actually initiating a new “generalised process of change” with outcomes arbitrarily described as ‘beneficial’ or harmful, but is not able to do what is required, namely “resolve an existing individualised process of change in particular patients”.
Extraordinary as it may seem, therefore, there does not appear to be any scientifically justified definition of beneficial effectiveness in orthodox medicine. Instead arbitrary specific measures are established for each trial or study, and the experience of clinical practice merely serves to increase this body of knowledge about the range of harm and ‘benefit’.
In contrast, homeopathy has identified a general ‘law of cure’ which is capable of being applied to a particular patient in order to determine if an intervention has been able to “resolve an existing individualised process of change”. As such it meets the criterion for measuring beneficial effectiveness, and offers a scientific approach to defining changes in health which can be tested objectively through experiment and in practice.
NHS Executive, Promoting Clinical Effectiveness - A framework for action in and through the NHS (London: NHS Executive, 1996) quoted by NHS Clinical Resource and Audit Group, Clinical Effectiveness Terms at http://www.crag.scot.nhs.uk/Glossary/terms.htm.
Henrik R Wulff, Stig Andur Pedersen and Raben Rosenberg, Philosophy of medicine: An introduction (Oxford: Blackwell Scientific Publications, 1986), p. 1.
William Alderson, Halloween Science (Stoke Ferry: Homeopathy: Medicine for the 21st Century, 2009), p. 88, available at http://www.homeopathyworkedforme.org/#/halloweenscience/4533482584.
Why it works