Heraclitus of Ephesus was a Pre-Socratic philosopher who lived during the 6th century BC. Heraclitus wrote a book which recorded his philosophical thoughts. This book, which was deposited in the temple of Artemis at Ephesus, has not survived in its entirety. Nevertheless, more than 100 fragments have endured the passage of time. Through these, the doctrines of the so-called weeping philosopher on universal flux, logos, and the unity of opposites have passed through the ages.