This dissertation has four parts. The first one is a general introduction into the topic of the work separated in a chapter that explains the used notation, a chapter that discusses typical examples, and a chapter that gives an overview of the three main parts. An important aspect of this first part is the attempt of a conceptual clarification of circularity, in particular in relation to the non-well-foundedness of a phenomenon. This clarification represents the philosophical core of the primarily formal dissertation. In the second part, Kripke's fixed point approach concerning partially defined truth predicates is examined: the algebraic foundations are introduced and problems of the construction are discussed. The main results of this second part are three characterization theorems of subclasses of interlaced bilattices and their applications. In the third part, revision theories are introduced. Their adequacy for the representation of circularity is discussed. Additionally, the complexity of these theories, the relation of revision theories to a wider thematic context, and their empirical properties are examined. In the last part of this dissertation, circularity is introduced on the level of set theory. The crucial idea is the concept of a coalgebraic modeling. In particular, the modeling of truth and the representation of the difference between private and common knowledge is emphasized. A comparison of the different accounts is provided in the last chapter.This dissertation has four parts. The first one is a general introduction into the topic of the work separated in a chapter that explains the used notation, a chapter that discusses typical examples, and a chapter that gives an overview of the three main parts. An important aspect of this first part is the attempt of a conceptual clarification of circularity, in particular in relation to the non-well-foundedness of a phenomenon. This clarification represents the philosophical core of the primarily formal dissertation. In the second part, Kripke's fixed point approach concerning partially defined truth predicates is examined: the algebraic foundations are introduced and problems of the construction are discussed. The main results of this second part are three characterization theorems of subclasses of interlaced bilattices and their applications. In the third part, revision theories are introduced. Their adequacy for the representation of circularity is discussed. Additionally, the complexity of these theories, the relation of revision theories to a wider thematic context, and their empirical properties are examined. In the last part of this dissertation, circularity is introduced on the level of set theory. The crucial idea is the concept of a coalgebraic modeling. In particular, the modeling of truth and the representation of the difference between private and common knowledge is emphasized. A comparison of the different accounts is provided in the last chapter
