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Aristotle (384—322 bc)


Erasistratus (c. 304—250 bc)

Hippocrates (c. 460—377 bc) Greek physician, traditionally regarded

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Greek and Roman scientists did not refer directly to the experimental method. However, in a variety of contexts they described testing procedures that were clearly deliberate investigations designed to throw light on problems or to support theories. Examples can be found in the Presocratic philosophers, the Hippocratic writers (see hippocrates ), Aristotle, Erasi‐stratus, Ptolemy 2, and Galen.

We should distinguish first the areas where experimental investigation is possible from those where it is not. Direct experiments in astronomy are out of the question. This was also true, in antiquity, in relation to most problems in meteorology (thunder and lightning) and in geology (earthquakes). In such cases ancient scientists often conjectured analogies with other more accessible phenomena that were directly investigable. Some of the experimental interventions described in the Hippocratic writers incorporate an element of analogy. The writer of Diseases 4 describes a system of intercommunicating vessels which can be filled or emptied by filling or emptying one of them. He uses this to explain the movements of the humours between the main sources in the body (stomach, heart, head, spleen, liver). What this shares with an experiment is the careful construction of an artificial set‐up. Where it differs from experiment in the strict sense is that its relevance to the physiological problem discussed depends entirely on the strength of the analogy suggested (in this case a mere conjecture).

Sometimes, however, direct interventions are proposed. Examples can be given from physics, harmonics, optics, physiology, and anatomy. Thus Aristotle states that he has proved by testing that sea water on evaporation becomes fresh: however, he then goes on to claim that the same is true of other flavoured liquids including wine—a typical risky extension of an experimental result.

Optics provides one of our fullest examples of a series of careful experiments, though the results have been adjusted to suit the general theory proposed. In his Optics Ptolemy describes his investigations of refraction between three pairs of media (from air to water, air to glass, and water to glass). He describes the apparatus used and records the results to within a half degree for angles of incidence at 10‐degree intervals. However, the results all exactly confirm a general ‘law’. Elsewhere he provides convincing experimental proof of the elementary laws of reflection, to establish, for instance, that the angle of incidence equals the angle of reflection.

Experiments in the strict sense were attempted also in the life sciences. Erasistratus described one in which a bird is kept in a vessel without food for a given period of time, after which he weighed the animal together with the visible excreta and compared this with the original weight. This he took to show that there are invisible effluvia from animals—again an overinterpretation of a correct result. Galen used experimental vivisections on animals to investigate various problems. He showed the peristalsis of the stomach in one, and produced a detailed account of the courses of the nerves in systematic experiments on the spinal cords of pigs. In the latter case no general theory is at stake: what the experiments reveal is the precise connection between vital functions and particular nerves.


Subjects: Classical Studies.

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