Heraclitus - Greek philosopher; first of the Greeks to develop a theory of the human soul; he praised its creative resources and spoke of the importance of self-exploration; he spoke of the logos that is common to all and said that the universe is ruled by logos; he always urged that close attention be given to the polarites and concealed structures emodied in language.
His famous claim that an idividual can and cannot step into the same river twice reveals an interest in criteria of unity and identity; even though all material constituents have undergone change, it is still, in a sence, the same river.
His theory that the earth exerted a magnetic influence throughout the solar system was a precursor to the modern conception of gravity as an attracting force between masses.
Gilbert was among the first to divide substances into electrics (spar, glass, amber) and nonelectrics.
In the 1600' Galileo and Kepler began to develop the physics that would prove Copernicus right.
William Gilbert - Some say (1544-1603) - English physician; known for his early studies on electricity and magnetism.
His De magnete (1600) propounded the theory that the earth was a giant lodestone with north and south magnetic poles.
The 12-chapter treatise included 292 woodcult illustrations carfully executed by Blasius Weffring.
Agricola also wrote a number of works on medicine, geology, mineralogy, politics, and economics.