I defined the true truth as the signifying derivative dS/dt . But what about the other combinations: the false truth, the true falsity and the false falsity? Slavoj Žižek have already distinguished between the false truth (lying in the guise of truth) and the true falsity (telling the truth in the guise of a lie):
one can lie in the guise of truth (this is what obsessionals are doing when, in statements which are factually entirely accurate, they conceal or disavow their desire); one can tell the truth in the guise of a lie (the hysterical procedure, or a simple slip of the tongue which betrays the subject’s true desire). (The Fragile Absolute)
The false truth of the obsessional consists of the fantasmatic ‘alternative facts’ which are constructed as a result of the concealment of desire, whereas the true falsity of the hysteric consists of the symptoms in which the repressed desire returns. In both cases, desire refers to the signifying derivative dS/dt of the ‘true truth’. The ‘false truth’ of the obsessional negates the fickleness of the adjective and sticks to the security of the noun, whereas the ‘true falsity’ of the hysteric negates the smothering noun and takes part in the bang of the adjective. And what about the ‘false falsity’?
A neurotic can be reliably addressed as an interlocutor: The analyst can hold onto either the constructed truth of a fantasy (as in the case of the obsessional) or the trueness manifested by a symptom (as in the case of the hysteric). But a false falsity negates both the noun and the adjective of the true truth. This is the case of the psychotic’s delusion in which both truth and trueness are lost, and there is no way to reliably address him/her as an interlocutor. The false falsity of a delusion is dominant in the psychotic, but it is not absent in the neurotic or the pervert.
The false falsity is permanently present in everyone as a dark shadow. It is what we call enjoyment. The lingering of this ghostly shadow is the inevitable cost of the sacrifice of the true truth in the name of reality. The superego injunction “Enjoy!” imposes the false falsity at the cost of the true truth. What’s more, the superego instigates the sacrifice of the true truth ‘just for fun’, without thereby establishing the factual reality which would be the favorable outcome of this sacrifice.
The real will  sacrifices the sacrifice and saves the true truth. The real will can only prevail by having a strong perceptivity about the false falsity of enjoyment in order to discern it from true desire. To be able to establish facts by ensuring fidelity to its true desire, the real will must avoid establishing fakeds (the temptation of illusions) as well as establishing fuckeds (the temptation of enjoyment) .