According to Schur, Freud's disturbance on the Acropolis was determined by guilt toward Fliess from whom he was withdrawing. Freud had received an angry letter from Fliess accusing him of plagiarism shortly before starting his trip in August, 1904; the effects of this letter must have been reverberating in him at the time of the derealization experience. The emphasis on the childhood relationship with the father is understood as a defense against the current conflict with Fliess.