1601-1650

King James I of England and Scotland: Photo by Imagno/Getty Images
Sir Walter Raleigh: Photo by Stock Montage/Getty Images
Sir Francis Bacon: Photo by Stock Montage/Getty Images
William Chillingworth: Photo by: Universal History Archive/UIG via Getty Images
Thomas Hobbes: Photo by DeAgostini/Getty Images
Roger Williams: Photo by The Print Collector/Print Collector/Getty Images

1651-1700

Margaret Cavendish: Photo by Bettmann/Getty Images
John Milton: Photo by Stock Montage/Getty Images
Ralph Cudworth: Image by Chronicle / Alamy Stock Photo
Gilbert Burnet: Photo by Universal History Archive/Getty Images 
Sir Isaac Newton: Photo by Imagno/Getty Images
John Locke: Photo by ullstein bild/ullstein bild via Getty Images
Title page from A Serious Proposal by Mary Astell: Public Domain

1701-1750

John Toland: Image by Paul Fearn / Alamy Stock Photo
George Berkeley: Photo by Kean Collection/Getty Images
Anthony Ashley Cooper 3rd Earl of Shaftesbury: Photo by Universal History Archive/Getty Images
Francis Hutcheson: Image by Granger Historical Picture Archive / Alamy Stock Photo
David Hume: Photo by Fine Art Images/Heritage Images/Getty Images

1751-1800

Jonathan Edwards: Photo by Bettmann/Getty Images
Lord Kames: Photo by Ken Welsh/*/Design Pics/Corbis via Getty Images
Adam Smith: Photo by Education Images/UIG via Getty Images
Thomas Paine: Photo by DeAgostini/Getty Images
Ethan Allen: Photo by Bettmann/Getty Images
Thomas Reid: Photo by Hulton Archive/Getty Images
Jeremy Bentham: Photo by The Print Collector/Print Collector/Getty Images
Mary Wollstonecraft: Photo by The Print Collector/Getty Images

1801-1850

Lord Byron: Photo by Raphael GAILLARDE/Gamma-Rapho via Getty Images
Lord William Thomson Kelvin: Photo by Universal History Archive/UIG via Getty Images
Jeremy Bentham: Photo by The Print Collector/Print Collector/Getty Images
Francis Wayland: Photo by Kean Collection/Getty Images
Ralph Waldo Emerson: Photo by Stock Montage/Getty Images
Jeremiah Day: Image by ART Collection / Alamy Stock Photo
Ralph Waldo Emerson: Photo by Stock Montage/Getty Images
Karl Marx: Photo by Bettmann/Getty Images

1851-1900

Henry David Thoreau: Photo by DeAgostini/Getty Images
Charles Darwin: Photo by adoc-photos/Corbis via Getty Images
John Stuart Mill: Photo by © CORBIS/Corbis via Getty Images
John Stuart Mill: Photo by © CORBIS/Corbis via Getty Images
Karl Marx: Photo by Bettmann/Getty Images
Charles Peirce: Photo by JHU Sheridan Libraries/Gado/Getty Images
Oliver Wendell Holmes, Jr.: Photo by Bettmann/Getty Images
William James: Photo by Stock Montage/Getty Images
Francis Herbert Bradley: Image by Lebrecht Music and Arts Photo Library / Alamy Stock Photo
Thorstein Veblen: Image by Granger Historical Picture Archive / Alamy Stock Photo

1901-1950

W. E. B. Dubois: Photo by Bettmann/Getty Images
George Edward Moore: Image by Pictorial Press Ltd / Alamy Stock Photo
George Santayana: Photo by Bettmann/Getty Images
William James: Photo by Stock Montage/Getty Images
Bertrand Russell: Photo by Bettmann/Getty Images
John B. Watson: Photo by George Rinhart/Corbis via Getty Images
John Dewey: Photo by Bettmann/Getty Images
Alfred North Whitehead: Photo by © Hulton-Deutsch Collection/CORBIS/Corbis via Getty Images
William David Ross: Photo by Kurt Hutton/Picture Post/Hulton Archive/Getty Images
Gertrude Stein: Photo by © Hulton-Deutsch Collection/CORBIS/Corbis via Getty Images
B. Frederic Skinner: Photo by Nina Leen/The LIFE Picture Collection/Getty Images

1951-2000

Willard van Orman Quine: Image by Geoff A Howard / Alamy Stock Photo
Thomas Kuhn: Photo by Bill Pierce/The LIFE Images Collection/Getty Images
Philippa Foot: Photo by Steve Pyke/Getty Images
Richard Rorty: Photo by Marty Katz/The LIFE Images Collection/Getty Images
Bas van Fraassen: Photo courtesy of Bas van Fraassen
Hilary Putnam: Photo released by Dr. Putnam himself (as copyright holder) under the Creative Commons Attribution ShareAlike 2.5 license
Daniel Dennett: Photo by David Levenson/Getty Images