When I associated entropy with the virtual , some of my friends pointed out that Deleuze dismissed entropy as a “transcendental illusion” in Difference & Repetition. So I went on to read his passage about entropy. Deleuze indeed seems irritated by the notion of entropy but what he wrote about it sounds nothing like a straightaway dismissal:
The paradox of entropy is the following: entropy is an extensive factor but, unlike all other extensive factors, it is an extension or ‘explication’ which is implicated as such in intensity, which does not exist outside the implication or except as implicated, and this is because it has the function of making possible the general movement by which that which is implicated explicates itself or is extended. There is thus a transcendental illusion essentially tied to the qualitas, Heat, and to the extension, Entropy. (Difference & Repetition)
By using Kant’s term “transcendental illusion” in order to dismiss entropy, Deleuze blames our own epistemological limitations for the paradox of entropy. He thus intends to free the world itself from paradoxes, thereby showing “excess of tenderness for things of the world” (Hegel said this apropos Kant). From the Žižekian perspective, the paradoxical status of entropy is not a reason to dismiss it as an epistemological error. On the contrary, its paradox is ontological: Entropy is a key signifier that captures the negativity of the world. This is apparent even in Deleuze’s description: “[entropy] has the function of making possible the general movement by which that which is implicated explicates itself”. This description gives entropy quite an exceptional status: Deleuze sutures together the fields of implication and explication, intensity and extensity, by means of entropy. Entropy is Deleuze’s symptom.
Now let’s translate Deleuze’s description of entropy (“that which is implicated explicates itself”) into our terms: Entropy is the locus of retroactive realization (Nachträglichkeit, après-coup, afterwardsness) and that’s why entropy is associated with information . Having grounded his philosophy on positivity, it is no wonder that Deleuze was annoyed by the constant increase of entropy, and was quick to dismiss this negative notion. By contrast, Lacan embraces entropy as the key  to enjoyment and signification in Seminar 17:
When the signifier is introduced as an apparatus of jouissance, we should thus not be surprised to see something related to entropy appear, since entropy is defined precisely once one has started to lay this apparatus of signifiers over the physical world. (…) In fact, it is only through this effect of entropy, through this wasting, that jouissance acquires a status and shows itself. This is why I initially introduced it by the term “Mehrlust,” surplus jouissance. It is precisely through being perceived in the dimension of loss –something necessitates compensation, if I can put it like this, for what is initially a negative number– that this something that has come and struck, resonated on the walls of the bell, has created jouissance, jouissance that is to be repeated. Only the dimension of entropy gives body to the fact that there is surplus jouissance there to be recovered. And this is the dimension in which work, knowledge at work, becomes necessary, insofar as, whether it knows it or not, it initially stems from the unary trait and, in its wake, from everything that can possibly be articulated as signifier. (…) This is the hollow, the gap that no doubt a number of objects initially come and fill – objects that, in some way, are adapted in advance, designed to be used as stoppers. This is no doubt where a classical analytic practice stops, with its emphasis upon these various terms, oral, anal, scopic, not to mention vocal. These are various names by which we can designate, as an object, the a – but the a, as such, is strictly speaking what follows from the fact that, at its origin, knowledge is reduced to an articulation of signifiers. This knowledge is a means of jouissance. And, I repeat, when it is at work, what it produces is entropy. This entropy, this point of loss, is the sole point, the sole regular point at which we have access to the nature of jouissance. This is what the effect the signifier has upon the fate of the speaking being translates into, culminates in, and is motivated by. (…) This is where work begins. It is with knowledge as a means of jouissance that work that has a meaning, an obscure meaning, is produced. This obscure meaning is the meaning of truth. (Seminar 17)
Işık Barış Fidaner is a computer scientist with a PhD. Admin of Yersiz Şeyler (Placeless Things) blog, Admin/Editor/Curator of Žižekian Analysis, and one of the admins of “Žižek and the Slovenian School” group on Facebook. Twitter: @BarisFidaner
 See “Spatial and Combinatorial”
 Entropy is key as a means of decipherment, not decryption. See “Decryption and Decipherment”