Zurich, 11 August 1926

'I cannot persuade myself to glue together two things ... which have nothing to do with one another from a logico-mathematical point of view'.

Einstein comments on a paper by Gottfried Beck on quantum mechanics: 'Obviously it is particularly awkward to use quanta conditions together with equations of movement here, as in this instance the compatibility of the validity of the latter with the validity of the former seems incompatible [sic]'; he also doubts whether a particular equation 'embodies any particular reality in relation to quanta. I very much doubt it. On the other hand the construction of the left side of the equation is certainly freighted with deeper truth'. An equation which Einstein himself has established on the subject is hardly more satisfactory: 'It allows for no electrical masses free of singularities. Also, I cannot persuade myself to glue together two things (like the left and right sides of an equation) which have nothing to do with one another from a logico-mathematical point of view'. Einstein is resolved to return home the next day, as he aspires to rest and concentration: 'Also my wife no.2 [Elsa Einstein] has great need of moral support, as she is all alone with her hopelessly ill mother'.

Elsa Einstein's mother, Fanny Einstein (née Koch), was in fact also Einstein's aunt (being the sister of his own mother, Pauline; curiously, Elsa was also closely related to Einstein through her father, who was a first cousin of Einstein's father).