Abstract

In an almost forgotten passage of the Postenor Analytics (Bk I, ch. III) Aristotle argues against 'another school', according to which it is possible to proof things 'by each other and in a circle'. His logical refutation of this opinion became so dominant in the Western philosophical tradition, that the 'vicious circle' has always deemed a crime since. A scientific demonstration has to be built on firm premisses in order to deduce conclusions from them in a straight, ongoing proces, in which one does not have to return to the premisses for a reconsideration of them on the basis of their implications. Although Aristotle does not mention names, he in fact reacts against Plato and the mainstream of Greek thought, which stresses the essential circularity of human argumentation. In the first, the historical part of the treatise the roots of this circular logic are unearthed in the work of Heraclitus and Parmenides, who both defended a ring structure of their metaphysical explication of nature. Truth is described as well-rounded, because you can follow it in a circle, passing through each of its links in turn, back to your startingpoint. The association of circular motion with thought is fully present in the work of Plato, who speeks many times about the 'periforas tès dianoias' and the essential interdependance of our ideas. Not the theory of an anonymous alternative school but Aristotle's own rectilinear formal logic was the exceptional, untraditional standpoint, which, moreover, was in conflict with his explication of divine thinking as 'noèsis noèseôs'. In modern times Hegel, Nietzsche and Heidegger were the main representatives of an anti-Aristotelian attitude. All three reject the logical prohibition of the circular argument, because it is inadequate to the life of concrete scientific thinking. The path of science always turns around towards its origins and results in a correction of its fundamental hypotheses on a higher level. Circularity is considered as a hallmark of sound logical procedure, as a characteristic of excellence in human understanding. The famous 'hermeneutic circle' is interpreted as the modern equivalent of the Hegelian 'Kreislauf and the Greek ' to par'allèlôn'. In the second, the more systematic part of the text the circular nature of our cognitive and scientific behaviour is demonstrated along three different lines. Reflection on the natural language with its finite stock of words, whose meanings are structurally connected, leads us to the so called semiotical circularity. Natural language is a complex network in which circular argumentation is not only unavoidable, but even the only means of explication. We have to work with the material contained in our dictionary, in which the items are defined by each other. The second reason is constituted by the system-orientation of science. In science we try to systematize our knowledge by means of formalisations and abstractions. The development of science can be characterised as a succession of systems, in which every element gets its meaning from the whole organisation. If we accept systematicity as the arbiter of truth, our logic is anti-fundamentalistic and the path of our thought is in fact circular (or better : spiralistic). The third adstruction of our theory is afforded by the coupling, that is realised in a rational proof. We draw conclusions from the coherence of our perceptions, from the reciprocal implications of our ideas. Never any of our ideas is without the repercussions of the movements elsewhere in the field. When we proof something, we also disproof and correct our startingpoints at the same time. The tradition of the circular nature of human thinking is very old, but not antiquated. The accusation of committing a fallacy in the case of circularity in normal and in scientific thinking is unfouded. It is now the formal logicians turn to defend his claim