When a patient brings forward a sound and incontestable train of argument during psycho-analytic treatment, the physician is liable to feel a moment’s embarrassment, and the patient may take advantage of it by asking: ‘This is all perfectly correct and true, isn’t it? What do you want to change in now that I’ve told it you?’ But it soon becomes evident that the patient is using thoughts of this kind, which the analysis cannot attack, for the purpose of cloaking others which are anxious to escape from criticism and from consciousness. A string of reproaches against other people leads one to suspect the existence of a string of self-reproaches with the same content. All that need be done is to turn back each particular reproach on to the speaker himself. There is something undeniably automatic about this method of defending oneself against a self-reproach by making the same reproach against some one else. A model of it is to be found in the *tu quoque* arguments of children; if one of them is accused of being a liar, he will reply without an instant’s hesitation: ‘You’re another.’ A grown-up person who wanted to throw back abuse would look for some really exposed spot in his antagonist and would not necessarily lay the chief stress upon the same content being repeated. In paranoia the projection of a reproach on to another person without any alteration in its content and therefore without any consideration for reality becomes manifest as the process of forming delusions.
Sigmund Freud 1901 Fragment of an Analysis of a Case of Hysteria