Deleuze used the term virtual to refer to an aspect of reality that is ideal, but nonetheless real. An example of this is the meaning, or sense, of a proposition that is not a material aspect of that proposition (whether written or spoken) but is nonetheless an attribute of that proposition. Both Henri Bergson, who strongly influenced Deleuze, and Deleuze himself build their conception of the virtual in reference to a quotation in which writer Marcel Proust defines a virtuality, memory as "real but not actual, ideal but not abstract". A dictionary definition written by Charles Sanders Peirce, referencing the philosophy of Duns Scotus, supports this understanding of the virtual as something that is "as if" it were real, and the everyday use of the term to indicate what is "virtually" so, but not so in fact.[a][b]
Deleuze's concept of the virtual has two aspects: first, the virtual is a kind of surface effect produced by actual causal interactions at the material level. When one uses a computer, the monitor displays an image that depends on physical interactions happening at the level of hardware. The window is nowhere in actuality, but is nonetheless real and can be interacted with. This example actually leads to the second aspect of the virtual that Deleuze insists upon: its generative nature. This virtual is a kind of potentiality that becomes fulfilled in the actual. It is still not material, but it is real.
Deleuze argues that Henri Bergson developed "the notion of the virtual to its highest degree" and that he based his entire philosophy on it. In Bergsonism, Deleuze writes that "virtual" is not opposed to "real" but opposed to "actual", whereas "real" is opposed to "possible". This definition, which is almost indistinguishable from potential, originates in medieval Scholastics and the Medieval Latin word virtualis. Deleuze identifies the virtual, considered as a continuous multiplicity, with Bergson's "duration": "it is the virtual insofar as it is actualized, in the course of being actualized, it is inseparable from the movement of its actualization."
Another core meaning has been elicited by Denis Berthier, in his 2004 book "Méditations sur le réel et le virtuel" ("Meditations on the real and the virtual"), based on uses in science (virtual image), technology (virtual world), and etymology (derivation from virtue—Latin virtus). At the same ontological level as "the possible" (i.e. ideally-possible) abstractions, representations, or imagined "fictions", the actually-real "material", or the actually-possible "probable", the "virtual" is "ideal-real". It is what is not real, but displays the full qualities of the real—in a plainly actual (i.e., not potential)—way. The prototypical case is a reflection in a mirror: it is already there, whether or not one can see it; it is not waiting for any kind of actualization. This definition allows one to understand that real effects may be issued from a virtual object, so that our perception of it and our whole relation to it, are fully real, even if it is not. This explains how virtual reality can be used to cure phobias. Brian Massumi shows the political implications of this.
However, note that the writers above all use terms such as "possible", "potential" and "real" in different ways and relate the virtual to these other terms differently. Deleuze regards the opposite of the virtual as the actual. Rob Shields argues that the opposite of the virtual is the material for there are other actualities such as a probability (e.g., "risks" are actual dangers that have not yet materialized but there is a "probability" that they will).
The virtual is far more than a technical or communications term. Martin Luther argued in his writing The Sacrament of the Body and Blood of Christ—Against the Fanatics with other Protestants, most notably Zwingli, over the virtualism of the Christian Eucharist, in alignment with Catholic tradition, that the Eucharist was actually and not virtually the body and blood of Christ.
According to Massumi in "Parables for the Virtual", the virtual is something "inaccessible to the senses" and can be felt in its effects. His definition goes on to explain virtuality through the use of a topological figure, in which stills of all of the steps in its transformation superposed would create a virtual image. Its virtuality lies in its inability to be seen or properly diagramed, yet can be figured in the imagination.
- Virtual [Lat. virtus, strength, from vir, a man]: Ger. virtuell ; Fr. (1) virtuel; Ital. (1) virtuale. (1) A virtual X (where X is a common noun) is something, not an X, which has the efficiency (virtus) of an X. This is the proper meaning of the word; but (2) it has been seriously confounded with 'potential' which is almost its contrary. For the potential X is of the nature of X, but is without actual efficiency. A virtual velocity is something not a velocity, but a displacement; but equivalent to a velocity in the formula, 'what is gained in velocity is lost in power.' So virtual representation was the non-representation of the American colonies in the British Parliament, which was supposed to be replaced by something. So Milton asks whether the angels have virtual or immediate touch. So, too, the sun was said to be virtualiter on earth, that is, in its efficiency. (3) Virtual is sometimes used to mean pertaining to virtue in the sense of an ethical habit. Virtual knowledge: a term of Scotus defined by him (Opus Oxon., Pt. I. iii. 3) as follows: 'Quantum ad notitiam habitualem sive virtualem, primo expono quid intelligo per terminos. Habitualem notitiam voco, quando obiectum sic est praesens intellectui [i.e. to the thought] in ratione intelligibilis actua ut intellectus statim possit habere actum elicitum circa illud obiectum. Voco virtualem, quando aliquid intelligitur in aliquo, ut pars intellecti primi, non autem ut primum intellectum sive ut totale terminans intellectionem; sicut cum intelligitur homo intelligitur animal in nomine, ut pars intellecti, non ut intellectum primum, sive totale terminans intellectionem. Hoc satis proprie vocatur intellectum virtualiter, quia est satis proximum intellecto in actu. Non enim posset esse actualius intellectum, nisi esset propria intellectione intellectum, quae esse ipsius primi, ut termini totalis.' Virtual difference: a term of the doctrine of formalities set forth by Scotus, Opus Oxon. Pt. I. ii. 7. (C.S.P)
- The long quote in Latin embedded in Note a is translated by John van den Bercken into English in On being and cognition : Ordinatio 1.3, Fordham University Press, 2016
- Pearson, K. Ansell (1999). Germinal Life. The Difference and Repetition of Deleuze. London and New York: Routledge.
- Peirce, C.S. "Virtual." Dictionary of Philosophy and Psychology, ed. James Mark Baldwin. New York: Macmillan, 1902 (Vol. II, pp. 763-764).
- Deleuze (1966, 43).
- Deleuze (1966, 96-98).
- Deleuze (1966, 42-43, 81) and Deleuze (2002a, 44).
- "Online Etymology Dictionary".
- Shields, Rob The Virtual Routledge 2003.
- Brian., Massumi (2002). Parables for the virtual : movement, affect, sensation. Durham, NC: Duke University Press. ISBN 0822328828. OCLC 48557573.
- Deleuze, Gilles. 1966. Bergsonism. Trans. Hugh Tomlinson and Barbara Habberjam. NY: Zone, 1991. ISBN 0-942299-07-8.
- ---. 2002a. Desert Islands and Other Texts 1953-1974. Trans. David Lapoujade. Ed. Michael Taormina. Semiotext(e) Foreign Agents ser. Los Angeles and New York: Semiotext(e), 2004. ISBN 1-58435-018-0.
- ---. 2002b. "The Actual and the Virtual." In Dialogues II. Rev. ed. Trans. Eliot Ross Albert. New York and Chichester: Columbia UP. 148-152. ISBN 0-8264-9077-8.
- Christine Buci-Glucksmann, La folie du voir: Une esthétique du virtuel, Galilée, 2002
- Massumi, Brian. 2002. Parables for the Virtual: Movement, Affect, Sensation. Post-Contemporary Interventions ser. Durham and London: Duke UP. ISBN 0-8223-2897-6.
- "Origins of Virtualism: An Interview with Frank Popper conducted by Joseph Nechvatal", CAA Art Journal, Spring 2004, pp. 62–77
- Frank Popper, From Technological to Virtual Art, Leonardo Books, MIT Press, 2007
- Rob Shields, The Virtual Routledge 2003.
- Rob Shields "Virtualities", Theory, Culture & Society 23:2-3. 2006. pp. 284–86.