This article analyses the importance of Humboldtian theory of language and linguistic diversity, of translation and a plurality of good translations – a pantheon, not a church – for the aims and method of the collective work Dictionary of Untranslatables. A Philosophical Lexicon (2014, French original 2004). It focuses on the presentation of Aeschylus’ Agamemnon, which Humboldt describes as ‘untranslatable’ while translating it, and relies on the notion of energeia, the importance of which is also underlined by Heidegger. The article argues that philosophy has to become aware that it takes place not in concepts, but in words. These words, however, are different in different languages. That has huge implications for thinking and for philosophy, and these have to be considered by philosophers.