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Infection and immunity
Infection and immunity

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2.1  Origins of the scientific method

There are two reasons for looking at ‘lessons from the history of infectious diseases’ when discussing the origins of the scientific method.

The first is to describe the conditions in which infectious diseases flourished in the relatively recent past of a major western industrialised nation, and underline similarities with present-day locations where infections still cause millions of deaths.

The second reason is to describe two classic experiments that form the basis of modern day strategies for preventing infectious diseases. In different ways they each illustrate the fundamental features of what has become known as the ‘scientific method’.

The Oxford English Dictionary defines the scientific method as:

A method of observation or procedure based on scientific ideas or methods … that has underlain the development of natural science since the 17th century.

It is now commonly represented as ideally comprising some or all of (a) systematic observation, measurement, and experimentation, (b) induction and the formulation of hypotheses, (c) the making of deductions from the hypotheses, (d) the experimental testing of the deductions, and (if necessary) (e) the modification of the hypotheses.

(Our italics added.)

The key words in this definition are shown in italics.

Systematic refers to any procedure conducted according to a fixed, pre-determined plan. All scientific experiments are ‘systematic’ in that the methods, materials, conditions and the sequence of actions involved are clearly and precisely described, so that other scientists can exactly follow the ‘system’ used in the original experiment.

A hypothesis is a statement proposing an explanation for an observation, made on the basis of limited evidence, as a starting point for further investigation. It has sometimes been described as ‘an informed guess’ about what the explanation for the observation might turn out to be. A fundamental principle of every hypothesis is that it must be testable, i.e. capable of being strengthened or ruled out as a result of further investigation. Of course if it is ruled out, then modifications must be made.

The first step on this investigative journey takes you back to the industrial cities of England in the early 19th century (Figure 1).

Figure 1  Stockport viaduct about 1850, lithograph by A. F. Tait.