Factual relativism (also called epistemic relativism, epistemological relativism, alethic relativism, and cognitive relativism) is the philosophical belief that certain facts are not absolute but depend on the perspective from which they are being evaluated. It challenges the assumption that all facts are objective and universally valid. According to factual relativism, facts used to justify claims are shaped by social, cultural, or conceptual frameworks, making them subjective and relative.

Factual relativism is rooted in the idea that the standards for what counts as a rational belief can change depending on cultural or conceptual perspectives. This challenges the traditional view that there are objective, universal standards for determining what is true and rational.

There are three main ideas behind factual relativism. The first is that the justification of beliefs depends on the context they are observed from. This challenges the idea of objectivity. The second is that there are many different perspectives and ways of thinking, some of which contradict each other. Lastly, factual relativism says that no perspective is superior to another.

During the Scientific Revolution, Galileo and Cardinal Robert Bellarmine disagreed about how planets move. Each used a different system. A relativist would argue that there is no fact of the matter about which view is supported by the evidence because there are no standards as to what evidence is true. In contrast, an anti-relativist would say one theory is better supported by evidence than the other.

Philosopher Thomas Kuhn influenced discussion of factual relativism with his idea of scientific paradigms. He argued that what scientists consider facts depends on the dominant paradigm they work within. These paradigms can shift drastically during periods of scientific revolutions, which suggests that scientific facts are not fixed but relative to the paradigm they arise from.

In anthropology, scholars like Peter Winch have explored how factual relativism plays out in non-Western cultures, such as the Azande people, whose belief in witchcraft is seen as rational within the context of their culture. This shows how factual relativism can help explain the legitimacy of different standards based on cultural context. This sparked debates about whether it is possible to compare beliefs across cultures using a single standard of rationality.

One perspective compares scientific knowledge to the mythology of other cultures, arguing that science is merely a societal set of myths based on societal assumptions. In Against Method, Paul Feyerabend writes, "The similarities between science and myth are indeed astonishing" and "First-world science is one science among many". But it is debated whether Feyerabend intended these statements to be taken entirely seriously, as they may have been a critique of the claimed objectivity of science rather than a full endorsement of the idea that science and myth are equally valid.

The strong program in the sociology of science, in the words of founder David Bloor, argues that it is "impartial with respect to truth and falsity". Elsewhere, Bloor and Barry Barnes have said "For the relativist [such as us] there is no sense attached to the idea that some standards or beliefs are really rational as distinct from merely locally accepted as such." In France, Bruno Latour has claimed that "Since the settlement of a controversy is the cause of Nature's representation, not the consequence, we can never use the outcome—Nature—to explain how and why a controversy has been settled."