As more of the world's languages are described and compared, more absolute universals have joined the class of statistical tendencies. However, few have questioned the universality of the duality of patterning. Following Hockett, most linguists assume that in all human languages, discrete meaningless parts combine to form meaningful units that, themselves, recombine. However, an alternative interpretation, explored in this article, is that duality, like other proposed linguistic universals, is a statistical tendency reflecting a complex set of factors, and most centrally, the need for some minimal number of basic units that can recombine to yield a potentially infinite set of form-meaning correspondences. If this is the essence of duality, then we expect: languages where duality is not a central component of grammar; languages where most, but not all, utterances are decomposable into meaningless phonological units; and different types of phonological building blocks in different languages. These expectations appear to be confirmed by natural language data.