The Johansson/Heyting letters and the birth of minimal logic
Tim van der Molen

Abstract:
In 1935 and 1936 Johansson and Heyting exchanged a series of letters. This exchange inspired Johansson to develop his minimal logic which he ultimately published in an article in 1937. This report summarises Johansson's article and letters, and discusses a number of interesting details of the letters.