Nikolai Luzin and the problem of existence in mathematics

This paper presents excerpts of the discussion about the problem of existence for functions in each one of Baire’ s classes. First, it sets up the historical problem, introducing four existential categories, and then it shows Luzin’ s position and reframes it in terms of Cavaillès and Gardies’ theory of thematization. MSC2010: 00A30, 26A21, 03E15

Set theory and the analyst

This survey is motivated by specific questions arising in the similarities and contrasts between (Baire) category and (Lebesgue) measure - category-measure duality and non-duality, as it were. The bulk of the text is devoted to a summary, intended for the working analyst, of the extensive background in set theory and logic needed to discuss such matters: to quote from the Preface of Kelley [Kel]: "what every young analyst should know"

The Creating Subject, the Brouwer-Kripke Schema, and infinite proofs

Kripke's Schema (better the Brouwer-Kripke Schema) and the Kreisel-Troelstra Theory of the Creating Subject were introduced around the same time for the same purpose, that of analysing Brouwer's 'Creating Subject arguments'; other applications have been found since. I first look in detail at a representative choice of Brouwer's arguments. Then I discuss the original use of the Schema and the Theory, their justification from a Brouwerian perspective, and instances of the Schema that can in fact be found in Brouwer's own writings. Finally, I defend the Schema and the Theory against a number of objections that have been made