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**Gottlob Frege and Rudolf Eucken – persons in conversation in the emergence phase of modern logic.
(Gottlob Frege und Rudolf Eucken – Gesprächspartner in der Herausbildungsphase der modernen Logik.)**
*(German)*
Zbl 0846.01006

The paper investigates the relations between Gottlob Frege and his philosophical colleague at Jena, Rudolf Eucken (1846-1926), Nobel prize laureate in 1908. In 1879 Eucken suggested to promote Frege to the position of an extraordinary professor, hinting already at Frege’s Begriffsschrift which had been completed only three weeks before. In 1886 Eucken published a review of Frege’s Grundlagen der Arithmetik of 1884 [Philosophische Monatshefte 22, 421-422 (1886)]. By comparing Frege’s works with publications of Eucken, especially his Geschichte der philosophischen Terminologie [Leipzig (1879)], the author gives convincing plausibility arguments for the assumption that, beside the mentioned direct connections, Eucken was a major source for Frege’s philosophical thoughts. The author shows, e.g., that Eucken might have hinted Frege at Adolf Trendelenburg’s discussion of Leibniz’s characteristica universalis on which Frege relied when linking his Begriffsschrift to the tradition of Leibniz’s programme. Furthermore, Frege’s conception of the unity of thought and its expression can be traced back to Eucken. There is also good evidence that Frege used some of Eucken’s arguments against subjectivism and psychologism. Although their interests diverged after 1885 Frege seems still to have adopted from Eucken the terms “Färbung” and “Beleuchtung” of thought which he used in his paper “Über Sinn und Bedeutung” (1892). The paper under review shows that Frege was no isolated figure in the academic Jena of his time.

Reviewer: V.Peckhaus (Erlangen)

### MSC:

01A55 | History of mathematics in the 19th century |

03-03 | History of mathematical logic and foundations |