Lacan
'The imaginary is presented by Lacan as one of the three intersecting orders that structure all human existence, the others being the symbolic and the real'. Lacan was responding to ' L'Imaginaire, which was the title of the "phenomenological psychology of the imagination" published by Sartre in 1940, where it refers to the image as a form of consciousness'. Lacan also drew on the way 'Melanie Klein pushes back the limits within which we can see the subjective function of identification operate', in her work on phantasy - something extended by her followers to the analysis of how 'we are all prone to be drawn into social phantasy systems...the experience of being in a particular set of human collectivities'. 'While it is only in the early years of childhood that human beings live entirely in the Imaginary, it remains distinctly present throughout the life of the individual'.
The imaginary as a Lacanian term refers to an illusion and fascination with an image of the body as coherent unity, deriving from the dual relationship between the ego and the specular or mirror image. This illusion of coherence, control and totality is by no means unnecessary or inconsequential (as something that is illusory). 'The term "imaginary" is obviously cognate with "fictive" but in its Lacanian sense it is not simply synonymous with fictional or unreal; on the contrary, imaginary identifications can have very real effects'.
Read more about this topic: Imaginary (sociology)