It is argued that the tendency of psychoanalysis toward sectarianism, the inclination to isolate theoretical viewpoints from each other, rather than pluralism, the active engagement of differences, is a significant factor in the loss of influence psychoanalysis has suffered. A brief history is given of the fate of theoretical differences in the field to show the historical sectarianism of psychoanalytic thought. The contention is that the resulting inability of psychoanalysis to define itself, even as a pluralistic discipline, renders it vulnerable to the criticism that the field has little claim to be a branch of knowledge, or to achieve scientific status, even under the most liberal definition of that term. The contention is that the failure to engage differences openly bears a closer kinship to religion than human science. A plea is made for dialogue in the Heideggerean sense of openness to difference so that psychoanalysis can establish itself as a human science characterized by the pluralism of intellectual dialogue rather than the insularity of sectarianism.