— Primo Levi
Context: Translation is difficult work because the barriers between languages are higher than is generally thought … knowing how to avoid the traps is not enough to make a good translator. The task is more arduous; it is a matter of transferring from one language to another the expressive force of the text, and this is a superhuman task, so much so that some celebrated translations (for example that of the Odyssey into Latin and the Bible into German) have marked transformations in the history of our civilisation.
Nonetheless, since writing results from a profound interaction between the creative talent of the writer and the language in which he expresses himself, to each translation is coupled an inevitable loss, comparable to the loss of changing money. This diminution varies in degree, great or small according to the ability of the translator and the nature of the original text. As a rule it is minimal for technical or scientific texts (but in this case the translator, in addition to knowing the two languages, needs to understand what he is translating; possess, that is to say, a third competence). It is maximal for poetry...
As quoted in "Primo Levi and Translation" http://www.leeds.ac.uk/bsis/98/98pltrn.htm by David Mendel http://findarticles.com/p/articles/mi_qn4158/is_20070320/ai_n18738601/print, in Bulletin of the Society for Italian Studies (1998)