The first step in the investigation is to determine if the text is consistent within itself. The Diary contains an extraordinary number of inconsistencies.
Let us take the example of the noises. Those in hiding, we are told, must not make the least sound. This is so much so that, if they cough, they quickly take codeine. The "enemies" could hear them. The walls are that "thin" (25 March 1943). Those "enemies" are very numerous: Lewin, who "knows the whole building well" (1 October 1942), the men from the store, the customers, the deliverymen, the agent, the cleaning woman, the night watchman Slagter, the plumbers, the "health service," the accountant, the police who conduct their searches of the premises, the neighbors both near and far, the owner, etc. It is therefore unlikely and inconceivable that Mrs. Van Daan had the habit of using the vacuum cleaner each day at 12:30 pm (5 August 1943). The vacuum cleaners of that era were, moreover, particularly noisy. I ask: "How is that conceivable?" My question is not purely formal. It is not rhetorical. Its purpose is not to show astonishment. My question is a question. It is necessary to respond to it. That question could be followed with forty other questions concerning noises. It is necessary to explain, for example, the use of an alarm clock (4 August 1943). It is necessary to explain the noisy carpentry work: the removal of a wooden step, the transformation of a door into a swinging cupboard (21 August 1942), the making of a wooden candlestick (7 December 1942). Peter splits wood in the attic in front of the open window (23 February 1944). [...]