Presentism is a mode of literary or historical analysis in which present-day ideas and perspectives are anachronistically introduced into depictions or interpretations of the past. Some modern historians seek to avoid presentism in their work because they believe it creates a distorted understanding of their subject matter. The practice of Presentism is a common fallacy in historical writings. 
The Oxford English Dictionary gives the first citation for presentism in its historiographic sense from 1916, and the word may have been used in this meaning as early as the 1870s. The historian David Hackett Fischer identifies presentism as a fallacy also known as the "fallacy of nunc pro tunc". He has written that the "classic example" of presentism was the so-called "Whig history", in which certain eighteenth- and nineteenth-century British historians wrote history in a way that used the past to validate their own political beliefs. This interpretation was presentist because it did not depict the past in objective historical context, but instead viewed history only through the lens of contemporary Whig beliefs. In this kind of approach, which emphasizes the relevance of history to the present, things which do not seem relevant receive little attention, resulting in a misleading portrayal of the past. "Whig history" or "whiggishness" are often used as synonyms for Presentism, particularly when the historical depiction in question is teleological or triumphalist.
Presentism is the philosophical doctrine that only events and entities—and, in some versions of presentism, timeless objects or ideas like numbers and sets—that occur in the present exist. According to presentism, events and entities that are wholly past or wholly future do not exist at all. Presentism contrasts with eternalism and the growing block theory of time, both of which hold that past events, like the Battle of Waterloo, and past entities, like Alexander the Great's warhorse Bucephalus, really do exist, though not in the present; eternalism alone extends this to future events as well.
Saint Augustine proposed that the present is a knife edge between the past and the future and could not contain any extended period of time. This seems evident because, if the present is extended, it must have separate parts – but these must be simultaneous if they are truly part of the present. According to early philosophers, time cannot be both past and simultaneously present, so it is not extended. Contrary to Saint Augustine, some philosophers propose that conscious experience is extended in time. For instance, William James said that time is "the short duration of which we are immediately and incessantly sensible". Other early presentist philosophers include the Indian Buddhist tradition. Fyodor Shcherbatskoy, a leading scholar from the modern era on Buddhist philosophy, has written extensively on Buddhist presentism: "Everything past is unreal, everything future is unreal, everything imagined, absent, mental... is unreal... Ultimately real is only the present moment of physical efficiency [i.e., causation]."
According to J. M. E. McTaggart's The Unreality of Time, there are two ways of referring to events: the 'A Series' (or 'tensed time': yesterday, today, tomorrow) and the 'B Series' (or 'untensed time': Monday, Tuesday, Wednesday). Presentism entails that the A Series is fundamental and that the B Series alone is not sufficient. Presentists maintain that temporal discourse requires the use of tenses, whereas the "Old B-Theorists" argued that tensed language could be reduced to tenseless facts (Dyke, 2004).
Arthur Prior has argued against untensed theories as follows: the meaning of statements such as "Thank goodness that's over" is much easier to see in a tensed theory with a distinguished, present Now. Similar arguments can be made to support the theory of egocentric presentism (or perspectival realism), which holds that there is a distinguished, present Self.
In the modern theory of relativity, the conceptual observer is at a geometric point in both space and time at the apex of the 'light cone' which observes events laid out in time as well as space. Different observers can disagree on whether two events at different locations occurred simultaneously depending if the observers are in relative motion (see relativity of simultaneity). This theory depends upon the idea of time as an extended thing and has been confirmed by experiment, thus giving rise to a philosophical viewpoint known as four dimensionalism. However, although the contents of an observation are time-extended, the conceptual observer, being a geometric point at the origin of the light cone, is not extended in time or space. This analysis contains a paradox in which the conceptual observer contains nothing, even though any real observer would need to be the extended contents of an observation to exist. This paradox is partially resolved in Relativity theory by defining a 'frame of reference' to encompass the measuring instruments used by an observer. This reduces the time separation between instruments to a set of constant intervals.
Some of the difficulties and paradoxes of presentism can be resolved by changing the normal view of time as a container or thing unto itself and seeing time as a measure of changing spacial relationships among objects; thus observers need not be extended in time to exist and be aware, but rather they exist and the changes in internal relationships within the observer can be measured by stable countable events.
Presentism is also a factor in the problematic question of history and moral judgments. Among historians, the orthodox view may be that reading modern notions of morality into the past is to commit the error of presentism. To avoid this, historians restrict themselves to describing what happened, and attempt to refrain from using language that passes judgment. For example, when writing history about slavery in an era when the practice was widely accepted, letting that fact influence judgment about a group or individual would be presentist, and thus should be avoided.
Critics respond that to avoid moral judgments is to practice moral relativism, a controversial idea. Some religious historians argue that morality is timeless, having been established by God; they say it is not anachronistic to apply timeless standards to the past. (In this view, while mores may change, morality does not.) Others argue that application of religious standards has varied over time as well. Saint Augustine, for example, holds that there exist timeless moral principles, but contends that certain practices (such as polygamy) were acceptable in the past because they were customary, while they are neither customary nor acceptable at present. Others argue that historians as humans cannot truly be objective and so moral judgments will always be a part of their work. David Hackett Fischer, for his part, writes that while historians might not manage always to completely avoid the fallacy, they should at least try be aware of their biases, and write history in such a way that they do not create a distorted depiction of the past. 
Presentism has a shorter history in sociological analysis, where it has been used to describe technological determinists who interpret a change in behavior as starting with the introduction of a new technology. For example, scholars such as Frances Cairncross proclaimed that the Internet had led to "the death of distance," but most community ties and many business ties had been transcontinental and even intercontinental for many years.
- Historian's Fallacie, David H. Fischer, 1970, p.137
- Historian's Fallacie, David H. Fischer, 1970, p.139
- James, William (1890). The Principles of Psychology 1. New York: Henry Holt and Company. p. 631..
- Buddhist Logic 1, New York: Dover, 1962, pp. 70–1.
- Prior, Arthur (January 1959). "Thank goodness that's over". Philosophy 34 (128): 12–17. doi:10.1017/s0031819100029685.
- Petkov 2005.
- "A Selected Library of Nicene and Post-Nicene Fathers of the Christian Church", Philip Schaff, Vol III, pg. 289
- Barry Wellman, “Physical Place and Cyber Place: The Rise of Networked Individualism,” International Journal of Urban and Regional Research 25,2 (June, 2001): 227-52.
- Fischer, David Hackett. Historians' Fallacies: Toward a Logic of Historical Thought. New York: Harper Torchbooks, 1970.
- Spoerhase, Carlos. Presentism and Precursorship in Intellectual History. In: Culture, Theory and Critique 49 (2008), S. 49–72.
Balashov, Y; Janssen, M (2002), "Presentism and Relativity" (PDF), British Journal for the Philosophy of Science (preprint of article) (Pitt). Bourne, Craig (2006), A Future for presentism, Oxford: Oxford University Press, ISBN 978-0-19-921280-4. McKinnon, N (2003), "Presentism and Consciousness" (Geocities), Australasian Journal of Philosophy (Yahoo!) 81 (4): 305, archived from the original on 2009-10-26. Petkov, Vesselin (2005), Is There an Alternative to the Block Universe View?, Pitt. Rea, MC, "Four Dimensionalism" (PDF), The Oxford Handbook for Metaphysics, ND. Describes Presentism and how four dimensionalism contradicts it.