Virtual

The term virtual is a concept applied in many fields with somewhat differing connotations, and also, differing denotations.

The term has been defined in philosophy as "that which is not real" but may display the full qualities of the real. Colloquially, 'virtual' is used to mean almost, particularly when used in the adverbial form e.g., "That's virtually [almost] impossible".

Philosophy
Numerous philosophers have advanced conceptions of the virtual. Most prominent of these in contemporary philosophy has been Gilles Deleuze, who uses the term virtual to refer to an aspect of reality that is not material, but which is nonetheless real. An example of this would be the meaning, or sense, of a proposition, which is not a material aspect of that proposition (whether it be written or spoken) but is nonetheless an attribute of that proposition. Deleuze's concept of the virtual has two aspects: first, we could say that the virtual is a kind of surface effect produced by the actual causal interactions which occur at the material level. When one uses a computer, an image is projected on the monitor screen which depends upon physical interactions going on 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 other aspect of the virtual which Deleuze insists upon, which is its generative nature. The virtual is here conceived as a kind of potentiality that becomes fulfilled in the actual. It is still not material, but it is real. Perhaps an example would be becoming inspired by the meaning of a text. The difficulty of how these two aspects of Deleuze's notion of the virtual hang together forms the crux of Slavoj Zizek's Organs without Bodies, in which Zizek claims that Deleuze backs away from this problem by forming a partnership with Felix Guattari. In Bergsonism, Deleuze writes that virtually means "in principle." So, the virtual is not what something is as a matter of fact, but what it is in principle. It must be admitted that this definition is not overly helpful in arriving at a rigorous definition of the term, but it is an important reference in thinking about the way that Deleuze relates to the philosophical tradition. "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 pseudo-Latin "virtualis".

Recently this conception of the virtual has been challenged and another core meaning has been elicited by (Denis Berthier, "Meditations on the real and the virtual" — in French), based on uses in science (virtual image), technology (virtual world), and etymology (derivation from virtue — Latin virtus). At the same ontological level as "possible," "real," or "potential," "virtual" is defined as that which 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. It explains that virtual reality may be used to cure phobias — which remains contradictory in any conception for which the virtual is a kind of potential.

Computing and information technology
The word virtual has been applied to computing and information technology with various meanings. It is used of software systems that act as if they were hardware systems (virtual machine, virtual memory, virtual disk), of computer-generated simulations of reality (virtual reality), and of internet gaming environments wherein entire worlds are created (virtual world). Other applications of the word are being found constantly in this fast expanding field, such as virtual community, and virtual library.

Early motivations for applying 'virtual' to computers (i.e., virtualization) were sharing of actual devices by many users and coordination of multiple processes, as seen with the successful use of the virtual machine approach. Internet and communication technology fostered de-coupling of space where events happen, and storage technologies facilitate de-coupling of time between a message being sent and received. These technologies build the environment for virtual work in teams, with members who may never meet each other in person. Communicating by telephone and e-mail, with work products shared electronically, virtual teams produce results without being co-located.

Similarly, a virtual world is a type of habitation founded upon web technology that allows interactions for pursuits, such as economy and real estate.