The nominalizing -er suffix has been extremely productive throughout the history of English, and in Present-day English it has developed a wide range of base and referent types. Yet most formal linguistic treatments account satisfactorily for only a fraction of the types of -er nominals actually found. I propose a cognitive model which not only addresses the problems with verb-based forms that are encountered in other models, but includes an account of all the nonverb-based -er nominals as well.