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In November 2010, following an invitation by Claudio Majolino, I gave a presentation in the seminar *Formes et Trasformations *in Lille, on “Husserl’s Notion of Manifold: Beyond Cantor and Riemann”.

In my presentation I argued that the concept of *Mannigfaltigkeit* (variously translated as “manifold” or “multiplicity”) in Husserl has been given various interpretations, due to its shifting role in his works. Many authors have been misled by this term, placing it exclusively in the context of Husserl’s early period in Halle, while he was elaborating his habilitation essay into the *Philosophy of Arithmetic*, as a friend and colleague of Georg Cantor. However, at the time Husserl distanced himself explicitly from Cantor’s definition and was rather inspired by Bernhard Riemann’s work, having studied and lectured extensively on Riemann’s theories of space. Cantor generally used “manifold” simply as synonym for “*Menge*” (quantity), or “*Inbegriff*” (collection), thereby laying the foundations for set-theory. Indeed, in the mid 1890s he started calling his work *Mengenlehre* (“theory of quantities”), instead of *Mannigfaltigkeitslehre (“*theory of manifolds”).

Husserl is well aware of the differences between Cantor and Riemann, e.g. in the period of the *Philosophy of Arithmetic *he tells us:

By manifold, Cantor means a simple collection of elements that are in some way united. [. . . ] However, this conception does not coincide with that of Riemann and as used elsewhere in the theory of geometry, according to which a manifold is a collection not of merely united, but also ordered elements, and on the other hand not merely united, but continuously connected elements. (Hua XXI, p. 95 f.)

Husserl’s *Mannigfaltigkeitslehre* would then not be a Cantorian set-theory, but come rather closer to topology. Then, in the *Prolegomena*, Husserl introduces the idea of a pure *Mannigfaltigkeitslehre* as a meta-theoretical enterprise which studies the relations among theories, e.g. how to derive or found one upon another. When Husserl announces that in fact the best example of such a pure theory of manifolds is what we actually already have in mathematics, this sounds slightly odd and is a bit misleading. The pure theory of theories cannot simply be the mathematics underlying topology, but should rather be considered as a *mathesis universalis*.

Mathematics, according to its highest idea, is the theory of theory [

Theorienlehre], the most general science of the possible deductive systems in general (Hua CW X, p. 411)

Indeed, while this might not have been fully clear yet in 1900/1901, Husserl will later explicitly tie together the notions of pure theory of manifolds and *mathesis universalis*. The *mathesis universalis* in this sense is formal, a priori and analytic, as theory of theory in general. It is an analysis of the highest categories of meaning and their correlative categories of objects. In my paper I discuss the development of the notion of *Mannigfaltigkeit* in Husserl’s thought from its mathematical beginnings to its later central philosophical role, taking into account the mathematical background and context of Husserl’s own development.

The presentation has now been published in a French translation as “La notion husserlienne de multiplicité : au-delà de Cantor et Riemann” in *Methodos* and is freely available on-line.

spectralsubjects

said:Hi Carlo,

Another excellent post. Any chance of an English translation?

Simon

rotenotes

said:Reblogged this on eidetisch.

Carlos R. Tirado

said:I think you are precisely right in your interpretation of the Theory of Manifolds as a Mathesis Universalis. It is exactly what my mentor and colleague, Dr. G.E. Rosado Haddock discussed in his interpretation of Husserls Philosophy of Mathematics.

Carlos R. Tirado

said:But I think that the “Theory of Manifolds” or “Theory of Theories” (depending on the emphasis you want to give, e.g. from the point of view of ontology or of semantics) are beyond the Mathesis Universalis. This latter would be comprised of logic and mathematics as sister disciplines, whereas the former (whether we called it Theory of Theories or Theory of Manifolds) would be a higher form of abstraction that may be unreachable for mathematicians or logicians, but may well serve as a continuous ideal to aim for.