The secondary literature on the First (and last) Universal Races Congress, which convened in London in 1911, covers various angles, but this is the first extensive treatment I have seen of the Jewish aspect of the Congress, which is significant inter alia for the fact that Jewish progressives, from Felix Adler on down, played a central role in its very organization. It is not a stretch to understand why Jewish intellectuals, anxious over their own place in Western civilization, would be motivated to counter racism in all its forms against all its victims. At that moment the Jews of the Russian empire were in dire straits, but anti-Semitic agitation and violence could be found in one fashion or another all over the Western world, including Britain itself.
However, the Jewish intelligentsia did not line up uniformly in any political or metaphysical camp. In taking a position on the racial or non-racial character of the Jewish people, concerns over emphasizing similarities with their host nationalities or preserving the Jewish people as a distinct entity competed for ideological attention. The variable configuration of racial concepts and their application to various positions was the order of the day in any case, as can be discerned among the participants of all nationalities and 'races' in the Congress. The total elimination of race as a meaningful natural concept was the most advanced position, which few in general took regardless of their politics. We see a spread among Jewish intellectuals as well.
Another factor in the division of opinion is analogous to the first: the need to conform to the political prerogatives of host nations vs. the impetus to protest objectionable actions taken against colonial subjects or other minorities.
This essay contributes to an appreciation of the complexity of the ideological situation a century ago, and the complexity of this very landmark, historic anti-racist intellectual intervention.
Nowhere in this treatment is there any mention of Zamenhof. It is worth noting that, while his knowledge of the world and political thinking were severely limited, the conclusions Zamenhof came to in working his way through the Jewish question that consumed him, issued in a definitive rejection of 'race' as an objective natural concept. Without engaging evolutionary or ethnographic research or speculation, Zamenhof ejected all mystical and pseudoscientific notions of group identity. He could be considered a naive forerunner of the notion of 'imagined communities'. Zamenhof's reduction of group identity and difference to language and religion is untenable, but in the process of oversimplifying social reality he simply assumes the essential unity of the human race and reduces difference to historical circumstance.