The active/passive system of English grew out of a Proto-Indo-European (PIE) system where the fundamental distinction was between active and middle voices. The middle voice included within its functions the relationship that now would be known as passive. The PIE voice system is preserved in ancient Greek and Sanskrit, and in the former, the middle voice is used when the subject of the verb is somehow affected by what is denoted in the verb. Examples of such situations in English, including those having some formal distinction, are provided, and linguistic processes by which the middle voice may develop are proposed. There is evidence that the syntax of a language changes in three fundamental ways: (1) mechanical changes in other subsystems of the language upset the functioning of the syntactic system, (2) the syntax is changed by speakers along the lines of alternate strategies of getting the same things said. These changes that are the result of communication needs may get tangled with movements along mechanical lines and force (3) analogical reanalysis of the syntactic system. The development of the middle voice is discussed both in terms of these change mechanisms and in terms of the communication needs to which the middle voice addresses itself. (CLK)