In my .bib-file the language field is filled out in all entries.
As MWE, they all look (as expected) like:
@Collection{Bakker:Grammar,
editor = {Egbert J[an] Bakker},
gender = {sm},
title = {Grammar as Interpretation},
subtitle = {Greek Literature in its Linguistic Context},
shorttitle = {Grammar},
language = {english},
year = 1997,
series = {Mnemosyne. Supplementum},
number = 171,
publisher = {Brill},
location ={Leiden AND New York AND K{\"o}ln}
}
To print the bibliogeaphy I created this file
\documentclass[paper=a4,twoside,ngerman]{scrartcl}
\usepackage[LGR,T1]{fontenc}
\usepackage[utf8]{inputenc}
\input{ix-utf8enc.dfu}
\usepackage{savesym}
\usepackage{gfsdidot,gfsporson}
\savesymbol{og}
\usepackage[main=ngerman,greek,italian,frenchb,english,british,german]{babel}
\usepackage[GlyphNames,boldLipsian]{teubner}
\savesymbol{breve}
\savesymbol{aa}
\usepackage[osf,sc]{mathpazo}
\restoresymbol{pplj}{breve}
\usepackage{courier}
\usepackage[scaled=.9]{DejaVuSansCondensed}
\Lipsiantrue
\ifFamily{pplj}{porson}
\usepackage{textcase}
\usepackage{textcomp}
\usepackage{xpatch}
\usepackage[pdftex]{hyperref}
\usepackage[style=german, german=guillemets]{csquotes}
\usepackage[style=philosophy-modern, sortlocale=de_DE,
sorting=nyvt, autolang=hyphen, alldates=terse,
annotation=true, useprefix=true, language=ngerman,
datezeros=false, bibencoding=auto, pagetracker=spread,
publocformat= loccolonpub, backend=biber,
citetracker = constrict, ibidtracker=constrict,
opcittracker=constrict, idemtracker=constrict,
relatedformat=parens, clearlang=true]{biblatex}
\usepackage{moredefs}
\usepackage{lips}
\usepackage{ragged2e}
\usepackage[twothirds,nonegthinspace]{thinsp}
\usepackage[babel]{microtype}
\usepackage{fixltx2e}
After compiling it with biber --bblsafechars mybib and latex mybib.tex I get
Bakker, Egbert J[an]
1997 Hrsg., Grammar as Interpretation. Greek Literature in its Linguistic Context, Englisch, Mnemosyne. Supplementum 171, Leiden, New York und Köln: Brill.
But I don't want LaTeX to print the name of the language ("Englisch" in the example above) but to use it only for hyphenation, and though I've been trying everything I've been trying everything for several months, I only found ways either to put each entry in another otherlanguage-environment (by passing the option babel=other to biblatex) or suppress all infos about the language by putting all known languages in \DeclareRedundantLanguages{ngerman}{german,english,french,italian,british,franconian,vedic,malaysian ...}
Another idea was to change the language-field in the .bib-file to hyphenation, but I still got the name of the language in each entry.

biblatexdoes not uselanguagebuthyphenationto determine the hyphenation language, so you need to use the latter field. If you usebabel=other, you will have to load the languages inbabelthough. You might be OK withbabel=hyphen. So your best bet is to change thelanguagetohyphenationfields. If you want, there is an automatic solution to maplanguagetohyphenation. – moewe Nov 01 '13 at 19:07babel=hyphenand thehyphenationfield. Keep in mind thathyphenationtakesbabel/polyglossialanguage identifiers such asngerman,americanetc. – moewe Nov 01 '13 at 19:20babel=hyphen, then biblatex complained and I changed it toautolang=hyphen. But nothing changed, neither withbabel=hyphennor withautolang=hyphennor after replacinglanguage =withhyphenation =in the .bib-file. So the first step is to maplanguagetohyphenation(how do I do it?), but I don't expect it to solve the problem---at least not evenhyphenationinstead oflanguagein the (very large: 450 items) .bib-file could preventEnglischin the example above. – Alexander Wittmann Nov 01 '13 at 19:28babel=hyphen, in 2.8 and above it'sautolang(thoughbabelstill works). The new name for thehyphenfield islangid(though, again, the old one should still work). – moewe Nov 01 '13 at 19:36\AtEveryBibitem{\clearlist{language}}. See biblatex remove the eng. from citations – Alan Munn Nov 01 '13 at 19:40langid(I didn't know it) forlanguagein the.bib-file! Excellent---but what do I write in the.texfile in order to map thelanguagefield to thelangidfields in the.texfile? I do not want to rewrite the entire.bibfile. – Alexander Wittmann Nov 01 '13 at 19:46babellanguage name. One would normally writelanguage={german}, while it is better to go withhyphenation={ngerman}for new German orthography. – moewe Nov 01 '13 at 20:00language={ngerman}and mapped it togermanby writing\DeclareLanguageMapping{german}{ngerman}(I did the same withbritishandenglish). How do I automatic mapping??? – Alexander Wittmann Nov 01 '13 at 20:08