The philosophy of translation becomes most interesting, and most consequential, when the things being translated are themselves philosophical concepts.
The history of philosophy is a history of translation disasters and productive misreadings. When Greek philosophy was translated into Latin, logos became ratio or verbum, losing the Greek word's strange combination of "reason," "word," "discourse," and "cosmic order." When Aristotle's eudaimonia became the Latin felicitas and the English "happiness," something was lost: eudaimonia means something like flourishing or living well, and it is about an activity and a way of being, not a subjective feeling-state. The translation "happiness" leads generations of readers to misread Aristotle's ethics as a theory about how to feel good, when it is actually a theory about how to live well.
Barbara Cassin's dictionary catalogues dozens of these cases. The German word Stimmung means something like "mood" or "attunement" but also "tuning" (as in a musical instrument). and Heidegger uses it to mean the basic affective tone in which you encounter the world "Mood" misses it. "Disposition" misses it. "Attunement" is closer but sounds technical. Every English translation of Heidegger grapples with this, and most produce a different compromise.
The Russian sobornost means something like communal unity, the organic togetherness of a spiritual community, but it carries specific Russian Orthodox theological connotations and a critique of Western individualism that "community" and "solidarity" don't begin to capture. The Arabic tarab refers to a state of musical ecstasy or enchantment, specifically induced by Arabic classical music, that involves a collective response between performer and audience that has no English equivalent. The Finnish talkoot describes a form of communal work done together without pay as a community act, with a specific cultural spirit around it that "volunteering" and "barn-raising" both partially miss.
Cassin's provocative argument is that these untranslatables are not failures but philosophical resources. The places where translation is most difficult are the places where conceptual diversity is most visible. Instead of trying to eliminate untranslatables by finding approximate equivalents, we should dwell in the difficulty, use it to notice the assumptions embedded in our own language, and allow the foreign concept to challenge those assumptions. To genuinely sit with amae or Stimmung or tarab is to allow a different linguistic community's way of organizing experience to unsettle your own.
This is, in miniature, the philosophical practice of taking other cultures seriously not as primitive versions of your own but as alternative explorations of the space of human possibility. The philosopher Charles Taylor calls this fusion of horizons (borrowing from Gadamer): genuine cross-cultural understanding is not translation into your own terms but a mutual expansion in which both parties' conceptual horizons are enlarged by the encounter. It is not that you come to understand the foreign thing in your own terms. You come to understand that your own terms were less complete than you thought.