Perspective is the choice of a single point of view from which to sense, categorize, measure or codify experience, typically for sharing it with another. It can be interpreted as a visual, audio, or linguistic choice, depending on the sense which is to be addressed and the media used in sharing. Viewpoint is another word for this principle, with similarly broad interpretation
In Visual arts and mathematics the word perspective is used in a technical sense to denote a way of representing three-dimensional objects in the plane (of painting, photoimage, drawing) aimed at proper rendering of depth relationships, see perspective as graphical representation.
Dr. Kim Veltman, a biographer of Leonardo da Vinci, explains the evolution of this concept from medieval to Renaissance times as one tied to Christian philosophy and how it changed during this period. Medieval figures are effectively cartoons, the presence or absence of a given figure, and their perceived piety and pose of submission to authority either of God or King, is of primary importance. Therefore they are drawn tall, thin, to fit more to the scroll. As of the renewal of investigation of astronomy, medicine and technology, which began in the 15th century after the fall of Muslim Spain, there was a valid reason to think in terms of three dimensional models and representations.
This had begun, however, argues Veltman, with the sculpture and architecture and fertile imaginations of exploratory engineering that we associate with da Vinci and Michelangelo and others whose interest was in the arts and not the sciences. Perspective, he argues, began with shifts in human cognition and the way it was conceived in the vulgar languages (i.e. not Latin) which provided a wider variety of ways to describe colour, light or perspective itself.
According to Thomas Cahill, in How the Irish Saved Civilization: The Untold Story of Ireland's Heroic Role from the Fall of Rome to the Rise of Medieval Europe, a similar shift had taken place in literature about a millennium earlier, with the Confessions of Augustine. The sacred literature known in the 5th century which had been scattered and lost and burned in Europe, and preserved only in Muslim libraries, remained in Christian control only in Ireland, where the bookish tradition we today associate with the medieval Roman Catholic monk were perfected, and then spread back into Europe. But these had been co-opted by the Church itself - to better aid it in imposing it's own idea of God's eye view. In effect, "monopolizing" perspective.
The dual nature of psychological perspective in this period is demonstrated most ably by the two most famous works of Niccolo Machiavelli, The Discourses which attempts to look at the problems of the Renaissance state from the point of view of the classical civics, and The Prince, which looks at it strictly from the perspective of the aristocrat seeking to gain and to keep power, by whatever means. This was fairly typical of the Renaissance period, where there was a stark contrast of two officially-understood perspectives: that of the Church, and the State. Indeed, in the 10th century, they had been officially separated. There was no room left for the commoner's emotional perspective, which was defined as "sinful" or confined to family or women - also the realm of what remained of the pagan traditions the Church ignored or subordinated or suppressed.
Given this, the treatment that Galileo received at the hands of the Pope is easier to comprehend - at the very tail end of the Renaissance but before the Enlightenment, there was really no critical tradition of choosing one's own personal perspective, and investigating the cosmos with it, and sharing it equally with others as peers with no mediation by anything but the senses and measuring sticks and tools (including the infamous telescope which extended one's perspective and let one challenge official views of the heavens). Thus, when Galileo wrote Dialogues Concerning Two World Systems, as a contrast between the views of the worldly and commanding character Sagredo and a naive Simplicio dutifully repeating church doctrine, it was not difficult for the Pope's advisors to convince him that Galileo was mocking the Church and him with it - the Pope was Simplicio, since the worldly Prince was clearly Sagredo. In effect, every choice to take a personal point of view was being interpreted as a grab for power of either worldly or spiritual kind - nothing else.
This situation did not really change until the emergence of the modern novel - of which Don Quixote is the least controversial early example - and secular music which was to please its listeners, not necessarily to please God. These were largely 17th century innovations.
By this time, Isaac Newton had characterized optics and decided that he saw seven colours in the rainbow - whereas the Greeks had seen only three or four. Newton had matched these, adding indigo, to the seven-note scale of musical scales of his time. George Berkeley attacked this kind of imposition of self-perspective on an objective phenomenon, but this time it was not as effective as in Galileo's time. We "see" seven colours to this day - taking Newton's perspective - as did the 19th century physicists who had a very fixed idea of the importance of frame of reference, based on F=MA and laws of motion.
Relativity imposed another radical shift on the idea of perspective in the early 20th century - according to Alfred North Whitehead, this was nothing short of a revolution. The notion that the choice of a vantage point from which to perceive events, speed of one's travel, and so on, would make it impossible to have one single "highest" or "most central" point from which to view all events was crushing to the mind trained in 19th century expectations of an orderly, clock-like hierarchy of natural law. Bertrand Russell wrote a popular book, ABC of Relativity, to explain the new rules. In another shift of perspective, his own search for foundations of mathematics had had to be abandoned, as the assumption that set theory could serve as the core on which arithmetic could rest, was shattered. This too was an aspect of the loss of the assumption of a single objectively-real starting point for perception and cognition, to which all other starting points were inferior.
Jane Jacobs ascribes some of this to the shift from the Enlightenment idea, actually noted by Baruch Spinoza first, that natural law tended to impose a sort of uniformity on man and the world, and that all that was lacking was some "perfect" understanding and emulation of it. This was also a critical component of Islam, which in the 20th century began to renew as an "underdog" faith emphasizing its role as the Other to British Empire and other European dominators. However, it is hard to see how the general shattering of the intellectual core of (what Terence McKenna called) dominator culture directly affected "perspective" itself.
The artistic movements of impressionism, futurism and expressionism - especially cubism - were more obviously concerned with shifts of perspective. Their explicit rationale was to "break up" or challenge assumptions about perspective, perception, cognition, and the role of the observer, which was increasingly of concern to physics via quantum mechanics.
By the late 20th century, some movements were beginning to suggest that perspective was wholly a matter of identity. Feminism and Queer studies in particular took this idea to some interesting extremes, suggesting that the whole way that the world was perceived might depend on how one saw sexual and emotional affordance within it. For instance, the way that Queers might perceive sexual opportunity where others might perceive only military discipline, or women might perceive emotional needs or opportunities where men might see a competition, were influential in both the art and social sciences. Also, the notion of humans as having a monopoly on perspective was challenged - John Lilly dropped LSD and hung in a tank to talk to dolphins - paintings by gorillas and chimpanzees sold for high prices in art auctions. Perspective was a matter of identity, and identity, by and large, a matter of choice - sensory differences were being celebrated, not suppressed, although this had some chaotic effects.
Probably the most important observation of the 20th century regarding perspective, other than its relativity, however, was that human males and females did seem to have quite different inbuilt tendencies for abstraction and visual projection, and for scanning and picking out distinct patterns on surfaces. While these were trivial differences for the average individual, in a whole population, the exaggerated effects of these tendencies on the numbers at extremes helped explain why there were few female mathematicians or physicists, and few males who could keep an eye on ten children at once. Another shift of perspective: neither gender was inferior, but nor could they perfectly communicate their perspective to each other.
The turn of the millennium in 2001 after the fraudulent Y2K panic, lent itself to another shift of perspective. Many "millennial" books of history and cognitive science and theory of civilization were written and released at this time, seemingly attempting to solidify ideals of perspective based on ecology and diversity: sometimes called a natural point of view or a cognitive paradigm or a diversity society.
New ways of describing internal experiences were categorized and began to be shared as if they were just as objective as those previously seen as external: the gate control theory of pain, for instance, compiled words used to describe pain experience to enable comparison of this most inner and unique sense among persons, and anthropological linguistics was concerned with the use of words to describe color and the visual perception that actually creates it.
More radically, theories such as morphogenetic fields and creativity as the basis of human difference from "animals" began to be advanced to explain the choices humans had, and were not taking, in the transformation of planet ecology.
Probably the most profound shift of perspective at this time was in maps. The 20th century Dymaxion Map of Buckminster Fuller had shown the single "world ocean" in which all the continents floated, but at the expense of utter disconnection and fraying of the ocean's edges. Space photographs (knitted together from many separate photographs initially) showed however a single blue ball, and altered perspective again: Earth appeared small, alive, and worth protecting.
In 2002, the World Wildlife Fund and the National Geographic Society had released the map of Earth's 867 terrestrial ecoregions, organized into 8 roughly-continental ecozones. Other maps focused on ocean currents and the potential impact of climate change on them. The planet was no longer a surface to be mapped but rather, an environment in a homeorhetic state subject to radical shifts due to mankind's influence. (see Gaia philosophy and Ecological Footprint)
Meanwhile, the perspective of non-humans (especially fellow hominids) was increasingly reflected in documentary works that attempted, in a tradition pioneered by Jane Goodall, to convey the actual experience of these genetically near-identical beings to humans. Genetics had a major part to play in altering ideas of who had a perspective worth considering. By 2003 the notion of Great Apes as hominids was not controversial, nor the notion that they had both a culture, and might also be persons in a legal sense.