PLATO (B.C. 427 -374), whose name is so illustrious in philosophy has directly and indirectly largely influenced the course of intellectual development and scientific thought. Before Plato had become the disciple of Socrates, he had been a student of the philosophY of Heraclitus, one of whose prominent doctrines was that all things are in a state of ceaseless change, so that, for example, no one could ever be twice on the same river, inasmuch as the water is ever changing. About the age of twenty Plato became a disciple of Socrates, and continued so until the death of the latter, nine years afterwards. Plato then visited various countries, as Egypt, Persia, Sicily, and Italy. On returning to Athens he established his renowned school of philosophy amid the groves of Academus, near Athens; and this place has given a common title to schools of art, learning, and science throughout the world. Plato lived to an advanced age and left behind him many writings, now esteemed amongst the most precious legacies that antiquity has bequeathed to us.
It was the practice of Socrates to constantly seek for definitions of justice, beauty, and so on, and this of course implied that he thought that in some things at least there was something permanent. Plato managed in his famous doctrine of Ideas to reconcile and combine the conflicting views of Heraclitus and of Socrates. This doctrine gave rise aftenvards to endless disputations, which for the most part diverted men's minds from the observation- of nature.
Two other men with names greatly celebrated among the ancients may be referred to here, as representatives of what may be termed the Natural History group of sciences. One of them was a contemporary of Plato, the other was a pupil of Aristotle. The first is the famous physician HIPPOCRATES B.C. 470-375), to whom is attributed the foundation of medicine as a science. The healing of wounds and the cure of diseases is an art, and as such must have been practised in some form at a period coeval with the existence of mankind. The successful practice of this art depends largely upon knowledge of the causes, symptoms, and course of diseases, and upon a knowledge of the anatomy and physiology of the human body.