Writers on delusions, such as Karl Jaspers and Kräupl Taylor, have rather consistently seen certainty and incorrigibility of belief as two of their defining characteristics (Jaspers 1963, Kräupl-Taylor 1966, 1983, American Psychiatric Association 1987). In this paper we shall challenge this by now customary view. More specifically, we shall challenge this view as its applies to a particular sub-class of delusions: the delusions of patients suffering from schizophrenia. We shall, on the other hand, concede that certainty and incorribility of belief do indeed characterize another species of delusions, the delusions of delirious patients. Moreover, we shall admit that schizophrenic patients regularly claim that they are certain about their delusions or that they "know" some things to be the case that normal people would regard as delusional. We shall interpret these pervasive claims, however, as expressions on the part of schizophrenics that are motivated by a determination to believe something indubitably precisely because they both believe it and doubt it while they seek to eradicate their doubt. More simply put, their assertions of absolute conviction do not depict their actual experience but rather a desired one, an experience they seek to make real precisely by insisting that it is now real.