Church or sect? For French trade unions and socialist parties that seems to have always been the question. Two of the leading socialist leaders of the Third Republic, Jean Jaurès and Jules Guesde, even came to personally embody this choice. As their fellow socialist Charles Rappoport, who knew them both, wrote in his memoirs:

Trotsky described Jaurès as a “capacious spirit” with “a physical revulsion for all sectarianism” (Goldberg 1968, 329, his translation). In contrast, Jules Guesde was the “guardian of the dogma” for whom “all deviation inspired … the same horror as the Christian schism did Innocent III” (Willard 1991, 93; Lefranc 1963, 50).

Between 1884 and 1905, French socialists were organized as sects – the Guesdists, the Possibilists, the Allemanists, the Independent Socialists, the Blanquists, and the anarchists – fighting among themselves for influence with the unions. Then, in 1905, these socialist sects set aside their differences under the broad tent of Jaurès's ecumenical ministry – his intellectual synthesis of the competing “traditions” of French socialism. In 1920, this Jaurèsian synthesis unraveled: the French Communist party was founded in a schism of, in Lèon Blum's words, “the Old House.” To this day, the French Left remains fundamentally divided, albeit with important moments of alliance along the way – the Popular Front in 1936 and the Common Program in the 1970s.