Scientist of the Month

Compiled by Peter Ellis,
author of the exciting new CD-ROM,
People in Science.
Find out more at www.peopleinscience.com

In the last four hundred years scientists like Galileo, Newton, Lavoisier and Darwin rejected and replaced many of the ideas of the ancient Greek philosophers. Nevertheless the Greek thinkers have had a great influence on our science, and our culture still shows the evidence. No one had more to say on all areas of science than Aristotle.

Plato's Pupil

Aristotle was born in 384 BC in Macedonia in northern Greece. His father was a doctor who looked after the health of the king. At the age of seventeen, Aristotle travelled south to the great city of Athens to study with the philosopher Plato. Aristotle and his fellow pupils learned to observe and argue using reason and logic and they learnt about the ideas of earlier Greek thinkers such as Pythagoras, Empedocles, Democritos, Socrates and Plato himself. After twenty years, Plato died and Aristotle realised that the Academy was no longer the place for him. He travelled across the Aegean Sea to Assos in Turkey. Here he advised the King and taught philosophy and married the King's daughter. After three years Aristotle and his wife moved to the island of Lesbos where they stayed with a wealthy friend from the Academy. Aristotle observed the many interesting creatures that lived on the island.

Alexander's philosopher

At the age of forty-two, Aristotle returned to his home to teach Alexander, the fifteen-year-old son of King Philip. Six years later, Philip died and Alexander became king. Almost immediately he set off on his quest to conquer the known world starting with Persia. Aristotle returned to Athens and set up his own college or Lyceum. He gathered followers around him fired with enthusiasm. Their aim was to collect together all the knowledge of the world and to compile an encyclopaedia. The Lyceum had what may be the first library of written works by philosophers from Greece, Egypt and further east.

Aristotle was interested in every aspect of what we now call science. In chemistry he adopted an older idea that matter was made up four elements - earth, air, fire and water - which each had properties of warmth or cold and wetness or dryness. Aristotle thought that the properties of real substances were mixtures of the four elements. For instance a piece of wood when it burns reveals the four elements - the flames of fire, the smoke and fumes of air, the water that oozes and bubbles out and the earthy ash left at the end. Aristotle did not like the idea of atoms that Democritos had thought about. If matter was made up of tiny particles there must be spaces between them, spaces that would have nothing in them - a vacuum. Aristotle's refusal to accept the possibility that a vacuum could exist came from his ideas about forces. He said that non-living objects could have "natural" or "forced" motion. The natural motion of earth and water was downwards because they had "gravity" while air and fire always rose because they had "levity". An object was given forced motion when it was thrown into the air and Aristotle concluded that the speed of an object depended on the force acting on it - no force, no speed.

Many of his ideas seem odd to us today because modern science has shown them not to be the best explanation for what actually happens but in the biological sciences Aristotle seems to be more "up-to-date". This is because he observed living creatures and described what he saw. His descriptions are very detailed. For example his description of the formation of a chicken embryo in an egg is very accurate and precise.

Aristotle was very concerned about "causes". He said there were four causes. For example a chicken's "efficient" cause or origin, was the egg. Its "material" cause, or composition, was what made it up - the flesh and bones. The "formal" cause was the unique description of the object - the type of chicken. Lastly there was the "final" cause that described the purpose of the object - in the case of the chicken, to produce an egg.

Alexander succeeded in his quest but died very young and his empire immediately began to break up. Aristotle found that he was not welcome in Athens any longer so in 321 BC he left but died the following year. The Lyceum continued however and Aristotle's followers spread his ideas by word of mouth and by writings. The books were copied and translated into Latin and Arabic. From 600 to 1300 AD Islamic scientists used Aristotle's works and those of other Greek philosophers. During the Middle Ages they found their way into Europe and started a new interest in the sciences. The Christian Church adopted Aristotle's ideas saying that they had been inspired by God. It was difficult for scientists with new ideas to point out Aristotle's mistaken reasoning. It took people like Galileo, who performed experiments to test ideas, to convince their contemporaries of the success of new theories and set European science on a new course.

Many of the descriptions of Aristotle's life and work on the Internet are aimed at a level above that of school pupils, but some contain pictures of Aristotle and list his works.