A line engraving of the 5th century BCE Greek philosopher Heraclitus of Ephesus. (From the Wellcome Library of Portraits)
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Original image by Wellcome Images. Uploaded by Mark Cartwright, published on 18 May 2016 under the following license: Creative Commons: Attribution. This license lets others distribute, remix, tweak, and build upon your work, even commercially, as long as they credit you for the original creation. This is the most accommodating of licenses offered, in terms of what others can do with your works licensed under Attribution.