Freud's concept of the primary process, when confined to the selection of objects for the formation of dreams or symptoms, depends strongly on the concept of association, which in turn depends strongly on the logic of pars pro toto. An examination of how Freud saw the primary process selecting objects leads to the identification of an equivalence relationship as governing his model. This results in a logical understanding of how the primary process works in forming associations and choosing candidate objects for dreams and symptoms. The relationship of this result to the work of Matte Blanco is also discussed, and the insights of this paper are applied to defining Freud's concept of a complex.