Fascinating philosophies from the late 19th and early 20th century continue to provoke and inspire the thinkers of today. This volume takes a close look at important developments of the era, beginning with the work of Friedrich Ludwig Gottlob Frege, a German philosopher and mathematician, and ending with the French existentialist Jean-Paul Sartre, who argued for the primacy of perception. Other notable philosophers from the period include John Dewey, Alfred North Whitehead, Bertrand Russell, Martin Buber, Ludwig Wittgenstein, and Martin Heidegger. Their lives and works are explored in this volume and paired with photographic portraits.