Delusions are critical components in a number of mental disorders, schizophrenia foremost. What are they? The standard view is that they are a type of belief--a pathological belief. Unfortunately, the standard view does not consistently correspond to clinical practice, where the term 'delusion' often applies to non-beliefs. We review the case for saying that non-beliefs can count as delusions. We argue that delusions are complexes of higher and lower order attitudes. They constitute a distinctive type of failure of self-knowledge and self-management. We describe the relevant type. One of the conceptual implications of our view is that beliefs need not be central to delusions.