this was written in 1920 or later : demon- strably not earlier , for my father used for it scraps of paper pinned together , and some of these are letters to him , all dated in february 1920.~ the third text no doubt began as a fair copy in ink of the second , to which it is indeed very close at first , but became as it proceeded a com- plete rewriting at several points , with the introduction of much new matter , and it was further emended after it had been completed .