Eugen Bleuler formulated schizophrenia as a disjunctive category based on universal, dimensional phenomena that were regarded as pathognomonic of the disorder. In consequence, schizophrenia came to dominate diagnostic practice in American psychiatry. This report suggests that affective disorder has been formulated in a similar way, and with a similar result. The nature of disjunctive categories is examined and their replacement by conjunctive categories for schizophrenia and affective disorder is anticipated.