The cognitive distortions and the idiosyncratic thought content of depressed patients have been described by me in a previous article.2It was suggested on the basis of clinical observation that many of the phenomena in depression may be characterized in terms of a thought disorder. This conclusion was drawn from the consistent finding of systematic errors, such as arbitrary inferences, selective abstraction, and overgeneralization in the idiosyncratic conceptualizations of the depressed patients. The present paper will present a theoretical analysis of the thinking disorder observed in depressed patients. The formulations will be limited to a few broad areas in which the relevant clinical material was considered adequate to warrant a formal theoretical exposition. The discussion will be directed toward two salient problems: first, how the typical idiosyncratic content and cognitive distortions become dominant during the depressed phase; secondly, the relationship