Literally, painting is regarded as a medium in that it is a physical substance used to picture. There is a dichotomy where painting is framed as a use of a material (paint), as in "the result of applying paint or color."  And in another sense painting is defined as a vehicle for "the representing of objects or figures by means of colours laid on a surface; the art of so depicting objects."  This dichotomy is succinct with the literal outlines of a medium itself, understood as a "pervading or enveloping substance; the substance or 'element' in which an organism lives," as well as "an intermediate agency, means, instrument or channel."  In this light, painting is considered as if synonymous with the meanings if not the uses of such ideas as 'picture, work of art, image, canvas, oil, watercolor, and print.' This list exemplifies the duality of painting as a medium conditioned both as a form (oil, canvas) that representation is embedded in and as means that representation moves through (picture, work of art). As well the Encyclopedia of Aesthetics lists discussions of painting through movements in historical categories: Abstract Expressionism, Abstraction, Classicism, Contemporary Art, Expressionism, Formalism, Impressionism, Landscape, Pop Art, Portraiture, Renaissance Italian Aesthetics, Romanticism and articles on Visual Art, Russian Aesthetics, Suprematism, and Surrealism.
Historically, the ability to picture, or signify by likeness, was the chief identifying characteristic that guided painting in conception and practice. The culmination of this ability to represent is steeped in the advent and subsequent implications of perspective; which "refers generally to the devices used by painters to represent space on plane surfaces...The earliest written account of perspectival projection is found in the treatise De Pictura (1435) of Leon Battista Alberti, a Florentine humanist and architect. Alberti defined a painting as 'the intersection of a visual pyramid at a given distance, with a fixed center and certain position of lights, represented by art with lines and colors on a given surface.' This conception of painting as the transcription of an imaginary 'picture plane' suspended between the beholder and the viewed scene was revolutionary. It linked the art of painting to the sciences, in particular to medieval optics and to Euclidean geometry (p.478)."  Additionally, "In twentieth-century thought, painterly perspective, with its hypothesis of a fixed and stationary beholder, its respect for the evidence of the senses, and its endowment of a subjective point of view with objective validity, has in turn been repeatedly enlisted as an emblem for Western empiricism, rationalism, individualism, anthropocentrism, or relativism (p.480)."  These conditions of picturing hinged on historical contentions of the collapse between the subjectivity of the beholder and the objectivity of that which is pictured. The agent of picturing (Becoming) was considered to be one in the same as reality (Being). In this model, the fundamental identity of 'painting' is entirely engrossed in that of 'picturing.' In "The Age of a World Picture," Martin Heidegger posits, "the word 'picture' (Bild) now means the structured image (Gebild) that is the creature of man's producing which represents and sets before. In such producing, man contends for the position for which he can be that particular being who gives the measure and draws up the guidelines for everything that is (p.134)." 
This system of rationalized picturing posits aspirations traditionally understood to be aligned with a conception of medium as an instrument to uncover knowledge. In this vein, Plato's interest in the mimetic status of images laid the philosophical platform for painting to be regarded as a vehicle for transmission of such truths. With Parrhasius, "Socrates starts from the premise that painting is 'imaging/modeling of the visible world' (eikasia ton horomenon) and moves to overcome the painter's initial doubt whether visual mimesis can depict 'character 'through' its physical expression (p.101)."  Plato's sense of doubt lies in the capacity for painting to move beyond the realm of appearances to the realm of truth. "Socrates' questions to the artists focus on how we get, or whether we can get, from the design of a visual field ('shapes and colours') to the representation or expression of non-material properties (p. 101)."  For Plato, this 'expression of non-material properties' is equated with an image of truth and leads him to dismiss writing and painting for the more transparent form of spoken word. "I cannot help felling Phaedrus, that writing is unfortunately like painting; for the creations of the painter have attitude of life, and yet, if you ask them a question they preserve a solemn silence (p.278)." 
Certainly, the epistemological claims of perspective in painting instigated elaborate challenges and redirections serving broader aspirations centered on painting as founded on matters of visual perception. Arnheim, dependent on Gestalt thinking, characterizes a dynamic transaction between the subjective through and the objective in of painting. "When it depicts three-dimensional space, it squeezes depth into surface, thereby obtaining a dynamic effect. This effect is perceived as the effort to unfold distances where none are actually given. The compressed surface pattern, however, has a compositional organization and meaning of its own, and this surface image interacts in a dynamic counterpoint with the composition of the objects occupying the three-dimensional arena (p.113-114)."  Moreover, Goodman, posited a thorough effacement of the objectified subjective; "In general, he maintained that 'no degree of resemblance is sufficient' to establish a relationship of reference between picture and an object (p.50)."  Panofsky instigated (through Cassirer's 'symbolic form' and Kant's notion of "category") a process of "iconographic analysis" of the picturing in painting. For example, questions of the Last Supper are revealed on conscious literary precedents and unconscious intrinsic insinuations. "On this level, the subject of the painting is identified: its moment and place of enactment, the names of its actors, its historical precedents, and so forth.... The Last Supper might be read not only as a 'document' of Leonardo's personality but also as an expression of the worldview of the Italian High Renaissance (p.437-438)."  Cultural and historical painting categories like Pastoral, Genre, Portraiture, Religious, and Epic typify this contingency of the object and the subject. Merleau-Ponty organized the phenomenology of painting in relation to the structures of history and institutions on paintings capacity to liquefy the threshold between the "visible" and "invisible." "Painting is an intentional, nonetic-noematic act, and therefore referential, but a painting is not about itself as formal elements and relations on a canvas, nor is it about the history of painting, but about the visible world that is all too often invisible (p.205)."  Painting as holding the subject to be perception is epitomized in classifications systems reliant on form: Impressionism, Fauvism, and Cubism for example. Hence, contentions of perceptual picturing have saddled on aims to be defined in relation to other sign systems, sparking ontological considerations.
In the Preface to his Laocoon (1766), Lessing, before arguing for the distinction of painting from poetry, states that both "present us with appearances as reality." Lessing's distinction of painting and poetry as separate forms insinuates a relational definition not entirely suspending questions of reality but as well not levying the means for the ends. Underlining, Lessing's argument is the simultaneity intrinsic in painting as opposed to a linguistic system of notation; "It is an intrusion of the painter into the domain of the poet, which good taste can never sanction, when the painter combines in one and the same picture two points necessarily separate in time... It is an intrusion of the poet into the domain of the painter and a squandering of much imagination to no purpose when, in order to give the reader an idea of the whole, the poet enumerates one by several parts or things which I must necessarily survey at one glance in nature if they are to give the effect of the whole (p.91)."  The complex relationship of image and text has poignant grounding in the positioning of the 'through' with respect to the 'in' of medium. This comparison method suggests a reorientation of the implications surrounding appearances of reality. The disposition of Being is not beyond appearances, but in Aristotelian fashion, between or in them. Hence investigations of knowledge, turn to examinations of language. And painting is grounded within the language of the iconic (resemblance) generation of meaning [see symbol, index, icon]. This model acts like a model of models with great difficulty in equating the picturing capacities of one process of signification from another. "No method--semiotics, iconology, discourse analysis--is going to rescue us from this dilemma. The very phrase "word and image," in fact, is a way of signaling this. It is not a critical "term" in art history like the other concepts in this collection, but a pair of terms whose relation opens a space of intellectual struggle, historical investigation, and artistic/critical practice (p.56)."  In this regard, the tradition of abstract painting has come to be postured as holding its primary project as repressing or overcoming verbal language.
The ultimate aesthetic retort to the promises of Renaissance perspective is found in the promises of twentieth-century pure abstract painting. This is the reverse side of painting as picture, and the over embellished zenith of the perspectival revisions/upheavals perpetuated by theorists like Goodman and Merleau-Ponty. As Greenberg wrote in "Avant-garde and Kitsch;" "Picasso, Braque, Mondrian, Miro, Kandinsky, Bancusi, even Klee, Matisse and Cezanne derive their chief inspiration from the medium they work in. The excitement of their art seems to lie most of all in its pure preoccupation with invention and arrangement of spaces, surfaces, shapes, colors, etc., to the exclusion of whatever is not necessarily implicated in these factors (p.9)."  These claims exaggerate a dialectical relationship between different forms (painting and photography) and arenas of cultural production (avant-garde and kitsch), as well as dichotomies within painting such as: abstract versus representational, figural versus geometric, and intuitive versus rational.
Subsequently, the aim of Abstract Expressionist painting was to distinguish its process of signification from that of other forms of art (as well as verbal language) through an extreme focus on the inherent materiality of the act of painting. Intrinsic to the extinguishing of the picture (external signification) is his declared affirmation "to reject the purist's assertion that the best of contemporary plastic art is abstract. Here the purist does not have to support his position with metaphysical pretensions (p.23)."  This aimed to reorientate the very action of picturing (making) as encapsulating the notion of the essential nature of a picture itself. The painted object acts as an indexical trace signifying the conditions of itself as constituted by it's making: personifying McLuhan's dictum "the medium is the message."
Reshuffling Greenberg, Fried in his own rigid dialectic of "Art and Objecthood," attempted to establish the criteria of painting (art) as defined by a disposition of shape oppositional to minimalism and theatricality (objecthood). "Roughly, the success or failure of a given painting has come to depend on its ability to hold or stamp itself out or compel conviction as shape - that, or somehow to stave off or elude the question of whether or not it does so (p.14-15)"  [see objecthood]. Notably, in a theoretical wake of Benjamin's notion of the "aura" external and surrounding an artwork, Greenberg attempts to characterize the conditions of painting as contingent on the making of the work (before), while Fried shifts the emphasis to the literal reception of the work (after): "it is concerned with the actual circumstances in which the beholder encounters literalist work (p.15)."  Ironically, Fried and Greenberg were attempting to stave off ubiquitous relationships of media while reserving a similar, if not the same, exuberant philosophical allocation of subjective Being (in paint) as accessed through claims of an objectified transparent Becoming (through picturing). These formalist propositions marked the necessary and dire circumstances of painting to hold onto the authority as the figurehead of art by aiming to crystallize the facility to represent postured as total denial of pictorial convention.
Marcel Duchamp put forward a wider scope, conjecturing pictures as well as the paint as "readymades:" mere conventions. Practitioners like Mondrian and Ad Reinhart served to lay a foundation of painting systems that sought to make manifest the inherent conventionality of picturing: albeit with quite different strategies. In their own suggestions, these processes of systematization instigated the "death of painting," with the deployment of conventions not bound to the paint itself. Frank Stella's desire to "preserve the paint on the canvas as good as it is in the can," turned the locus of painting to the can itself framed as an industrial mass produced commodity of circulatory exchange instigating a reorganization of painting as a medium embedded in a field of cultural production. As Joesph Kosuth in "Art After Philosophy" wrote "With the unassisted Readymade, art changed its focus from the form of the language to what was being said. Which means that it changed the nature of art from a question of morphology to a question of function (p.842)."  In this light, currently painting takes a rearguard position negotiating itself as a system of media, within a system of media constituted by an abundant and dynamic matrix of images and corporeal realities. The most current debate of the viability of painting contends it as a critical post-mortem activity dealing with its own death and on the other hand as it reveling in its own frivolity ignoring prescriptive historical paradigms that both killed it and continue to define its potency.
Committee on the Visual Arts