In the 1970s and 1980s, literary theorists, particularly in the German-speaking world, showed increasing interest in appropriating the distinctive methodologies of both the positivist social sciences and the natural sciences. Alongside empirical (e. g. Groeben 1982) and analytical approaches to literature (e. g. Fink/Schmidt 1984), the structuralist school shaped by Lotman’s narrative theory attempted a scientific turn in literary theory (cf. Köppe/Winko 2010), aiming for an exact science, or at least one more exact than the traditional ›art of interpretation‹ admitted by Staiger (1955). We trace the structuralist approach, or more precisely, the central aspect of structuralist narratology, the theory of boundary-crossing, first in Lotman (1979), and then criticise Renner’s remodelling based on formal logic (1983), and finally remodel boundary-crossing theory by means of modal logic. By doing this, we hope to demonstrate the potential of a methodologically self-aware, terminologically precise text analysis that is therefore capable of intersubjectivity. At the beginning of the 1970s, the Estonian literary scholar and cultural semiotician Jurij M. Lotman took as his starting point the strong human affinity for the replication of abstract systems ( Ordnungen ) as spatial relationships. This principle is of great heuristic significance for Lotman, as it enables the use of the topological and topographic structures of a text to appraise their central, non-spatial content. Using this textual spatial structure, Lotman is able to define what is to be regarded as plot or action: the movement of a character in space. In addition, the spaces and the characters which are located in these spaces must be given non-spatial characteristics, so that the semanticised spaces and characters are placed in opposition to each other. For Lotman, such a case would constitute a boundary-crossing: the border, which establishes the opposing spaces and is in that sense impermeable, is crossed. Thus the movement of the character would constitute an event. An event is in turn the starting point for an intratextual discourse about the textual (world) system: previously, the world depicted was an ›ordered‹, systematised one, opposing characteristics having been clearly separated from each other. Now, however, the movement of the character brings the ordering of the text itself into movement, as direct ›confrontations‹ or ›collisions‹ of the opposed characteristics of space and character arise (Lotman 1973). It is thus shown that Lotman always considers systems of order in connection with deviation from that system. Hence, not only does the deviation contradict the order, the order contradicts the deviation. It is a reciprocal relationship, particularly when considered epistemologically: order is constituted against a background of deviation from that order. Systems of order only become relevant, that is to say gain a narratological function, when they are deviated from. The most influential formulation of Lotman’s boundary-crossing theory – at least in the German speaking world – was that of Karl N. Renner in the early 1980s. Renner understood events to be disruptions of order, and disruptions of order in turn as logical contradictions. In addition to the formal logic representation of disruptions of order, Lotman and Renner differ in that Renner presupposes that the ›eventful situation‹ arises and continues, i. e. that the eventful situation continues until the contradiction is once more resolved. However, Renner’s definition of the event as the arising of a logical contradiction and of the eventful situation as the continuation of that logical contradiction produces a grave problem: formal logic excludes the possibility of a contradiction because of the principle of non-contradiction. This follows from the fact that, in formal logic, a contradiction must always be resolved. The occurence of the event, therefore, demands its immediate termination – either through a change of the ordering statements which determine how a character should be or behave, or through a change of the description of the situation which determines how a character should be or behave. That, however, contradicts Renner’s understanding of the durative aspect of the event. The consequences of the principle of non-contradiction do not occur to Renner. While Renner is, in fact, dissatisfied with his model, for him the problem lies in a different circumstance: his ordering statements lack the characteristics of postulates. It can be deduced from his writings that he wishes his ordering statements to be understood as normative statements. However, non-modal sentences, and these are precisely what Renner uses, do not describe, even in the case of subjunctions/implications, what should be, but merely what is . Renner’s ordering statements, therefore, are equivalent in formal logic to his statements of description, with the sole difference that the ordering statements, because of their if-then form, are conditional actual-state statements: if x applies, then so does y. This is in no sense a normative statement. Renner, then, sketches out a model using ordering statements with the operators of necessity of modal logic, without being able to solve the problem he had correctly recognised. This problem, addressed but not explored by Renner, can be solved with the help of normative reasoning/deontic modal logic. Instead of an operator of necessity, here an operator of obligation is used. Using this operator, we can produce contradiction-free statements about how something should be, which can be placed in relation to selective statements about how things are. Our aim, however, is not exclusively or primarily to criticise Renner, but rather to develop the particular benefits which these consideration of formal logic bring to cross-boundary theory – namely the connection between the quality of the ordering statements, and the durative and non-durative aspect of events. We demonstrate this using Pierre Boulles’ 1963 novel La Planète des singes ( Planet of the Apes ). In the course of this exemplary analysis, we will show that our modified model of boundary theory is, on the one hand, capable of more exact differentiation and classification than the Lotman-Renner model. On the other hand, we can demonstrate the advantages of a procedure informed by formal logic. They lie precisely in those characteristics which are unique to formal logic: above all a maximum of exactness in the intersubjectivisation of the analytical process. Finally, we hope to show that our remodelled formal logic theory of boundary-crossing is in no sense a ›scientification of literary studies‹; it is not a fully developed method of interpretation but rather nothing more, and also nothing less, than a genuinely analytical approach to the diegesis of texts.