Heraclitus, << `hehr` uh KLY tuhs, >> was an early Greek philosopher active about 500 B.C. He regarded himself as having access to a central truth available to all people. However, people remained ignorant of this truth due to failure to use their senses and understand correctly. This truth is a unifying rational principle called the logos. Heraclitus asserted that everything in the world constantly changes and moves, a condition he called strife (flux). He believed that this unending motion ties together all opposing forces–such as hot and cold–in a delicate balance or state of tension. This underlying unity has come to be known as the unity of opposites.
Heraclitus thought that the unity and strife that make up the universe also govern human life. This unity appears most obviously in the tension between life and death and waking and sleeping. Heraclitus asserted that the world is a fire, which is a living symbol of the constant strife in the ordered world. The soul is fiery.
Heraclitus lived in Ephesus, a city in Asia Minor (now part of Turkey). He wrote one book from which about 130 fragments have survived. In ancient times he was known as the Obscure because of the difficulty of his thought. See Pre-Socratic philosophy .
