What an amazing man Aristotle was! He lived in the third century BC yet he was so influential that his ideas dominated western scientific thought for almost two thousand years. This is especially remarkable in light of the fact that most of his notions about the workings of the world were completely wrong. But in spite of this, Aristotle is widely regarded as the first real scientist. Why?
Above all, Aristotle was an incredibly curious man. He wanted to find out everything that could be known about the natural world. "Through wonder, philosophy begins," he wrote and thereby dedicated himself to unravelling the mysteries of life. This quest was by no means a new idea. Others before had certainly been mystified by the workings of the world. But they mostly subscribed to the philosophy of thinkers like Socrates who believed that the fundamental nature of the world could be discerned by mental reflection alone.
But this was not good enough for Aristotle. For him, the basis of all knowledge was experience. Explanations were only valid if they were induced by observed phenomena. In other words, theories should be formed starting with facts. And this idea is of course at the core of the scientific method.
Aristotle's contribution to science is perhaps best demonstrated by his classic description of the growth of a chick inside an egg. How a chick hatches from an egg was not to be determined by philosophy, but rather by a simple experiment. Eggs were to be placed under hens and opened in sequence, one each day. It quickly became apparent that the embryo appears after three days and that the chick grows in the white of the egg, nourished by the yolk. A theory of what happens inside of an egg could now be formulated based on facts! He even concluded that the earth was round based on his observation that the top of the mast was the first part of a sail boat to be seen from the shore.
In many cases, however, Aristotle's theories, though consistent with observed facts, turned out to be quite wrong. He was a strong believer in the theory of the elements as had been put forward by Empedocles, namely that everything in the world was somehow composed of air, water, earth and fire. This certainly seemed to fit Aristotle's observations. When a green twig was burned, it released fire, produced "air" in the form of smoke, water in the form of sap and left an "earth" in the form of ashes behind. A logical theory, based on facts, but very wrong!
According to this theory, when arsenic and sulfur, two substances known to the Greeks, combined under the influence of heat, the product was a novel substance in which arsenic or sulfur no longer existed. This made sense because the physical properties of arsenic sulfide are certainly different from its component elements.
Aristotle also studied the lungs and concluded that their purpose was to cool the body by circulating air inside, much like bellows. He also believed that insects were spontaneously generated by putrefying vegetable matter and that the earth was the center of the universe. These theories, although wrong, could all be supported by observation.
But the great man had some ideas that were truly bizarre. He maintained that the semen of youths below the age of twenty one could not lead to fertility. This hypothesis of course could have been easily tested and shown to be incorrect. Like other Greeks of the times, Aristotle believed that women were mentally and physically inferior to men.
So how is it then, that this melange of some correct, some quirky but mostly wrong ideas dominated western thought for so long? Mainly because Aristotle provided logical and common sense explanations for everyday experiences. These he expressed so authoritatively and convincingly that generations of followers found it easier to believe Aristotle than to put his notions to an experimental test. Today, we still see this "Aristotle effect" in the reliance of some people on convincing sounding quackery.
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