Einstein wrote, “I attach special importance to the view of geometry which I have just set forth, because without it I should have been unable to formulate the theory of relativity. Without it the following reflection would have been impossible:-“

Albert Einstein gave an address on 27 January 1921 at the Prussian Academy of Sciences in Berlin. He chose as his topic Geometry and Experience. He lectured in German but we present an English translation below. The lecture was published by Methuen & Co. Ltd, London, in 1922. https://mathshistory.st-andrews.ac.uk/Extras/Einstein_geometry/