Although Buisson was a philosopher by education, he preferred to devote his life to working with children, and to the issues of secular education as well as separation of church and state. He opened the first secular orphanage in 17th Arrondisement in Paris.

In 1890 Buisson became professor of pedagogy at the Sorbonne and, subsequently, a campaigner for French secularism as the leader of the parliamentary committee drafting the law on separation of church and state in France (1905). The principles laid out in the law are still binding and constitute one of the cornerstones of the Republic.

In 1898, during the famous Dreyfus case, Buisson supported the slandered Jewish captain. Later he co-founded the French Human Rights League, which he presided over from 1913 to 1926. As a member of parliament (1902-1924, with breaks) he was a proponent of voting rights for women.

Quidde’s activities span four periods in the history of Germany: from Chancellor Bismarck through the Hohenzollern Empire and Wilhelm II, the Weimar Republic to Hitler’s Third Reich.
He came from a well-to-do family of merchants from Bremen. While studying history Quidde became fascinated by pacifism, and in 1894 he wrote a short essay on the Roman Empire in the times of Caligula, which in fact was a critical satire on the rule of Emperor Wilhelm II. The publication of the pamphlet and notes explaining the parallels between Caligula and Wilhelm II put an end to Quidde’s academic career.

After Hitler’s rise to power in 1933 Quidde left for Switzerland. He spent the rest of his life in Geneva, invariably remaining optimistic about the future of mankind. Although during his lifetime militarism was seen as superior to any other ideology, Quidde believed that modern technologies could prevent wars.