Is anonymisation possible?

In today's world of rapidly evolving digital technology, guaranteeing the anonymity of a psychoanalytic patient in a published paper is very much harder than it may seem. Anonymisation in publishing is part of a wider problem of psychoanalytic confidentiality. Identifying details can be changed but information relating to external reality may still be present in the text. The risk of deanonymisation often cannot be estimated and is instead subject to radical uncertainty. The paper considers various sources of this radical uncertainty. Anonymisation of a patient may need to remain effective for decades. The conditions for ensuring this are exacting and rarely likely to be met in practice. Possible consequences of abandoning belief in the safety of anonymisation are briefly considered.