The hypothesis that phonological patterns are at least in part explained by functional phonetic considerations has a long history. Yet the role that functional notions have played in the history of generative phonology can be described as indirect and peripheral, at best. This article focuses on a single allophonic rule of Russian, a rule by which /i/ is said to emerge as [ɨ] after plain (non-palatalized) consonants. One goal of this paper is to argue for a significantly different understanding of the generalization. Specifically, nonpalatalized consonants before i are velarized. At a more theoretical level, the paper advocates the goal of seeking explanations for allophonic processes, particularly non-assimilatory ones, rather than simply stating them or focusing on questions of distribution. In the case examined, and perhaps many others, the explanation depends on functional considerations, in particular the requirement that contrasts be sufficiently distinct. Most broadly, these results imply that the terminological distinction between ‘contrastive’ or ‘phonemic’ on the one hand and ‘allophonic’ on the other conceals a deeper unity between the two: allophonic processes at least sometimes serve the goal of contrast preservation.