Generally, a fact is something that is the case, something that actually exists, or something that can be verified according to an established standard of evaluation. There is a range of other uses, depending on the context. Philosophers and scientists are interested in facts because of their relation to truth.
Etymology and usage
The word fact derives from the Latin Factum, and was first used in English with the same meaning: "a thing done or performed", a use that is now obsolete.
The common usage, "something that has really occurred or is the case", dates from the middle of the sixteenth century. Fact is also synonymous with truth or reality, as distinguishable from conclusions or opinions. This use is found for instance in the phrase Matter of fact, and in "... not history, nor fact, but imagination."
Fact also indicates a matter under discussion deemed to be true or correct, such as to emphasize a point or prove a disputed issue; (e.g., "... the fact of the matter is ...").
Alternatively, "fact" may also indicate an allegation or stipulation of something that may or may not be a "true fact", (e.g., "the author's facts are not trustworthy"). This alternate usage, although contested by some, has a long history in standard English.
Fact may also indicate findings derived through a process of evaluation, including review of testimony, direct observation, or otherwise; as distinguishable from matters of inference or speculation. This use is reflected in the terms "fact-find" and "fact-finder" (e.g., "set up a fact-finding commission").
Fact in philosophy
In philosophy, the concept fact is considered in epistemology and ontology. Questions of objectivity and truth are closely associated with questions of fact. A "fact" can be defined as something which is the case, that is, the state of affairs reported by a true proposition.
Facts may be understood as that which makes a true sentence true. For example, the statement "Jupiter is the largest planet in the solar system" is made true by the fact that Jupiter is the largest planet in the solar system. Facts may also be understood as those things to which a true sentence refers. The statement "Jupiter is the largest planet in the solar system" is about the fact that Jupiter is the largest planet in the solar system. Fact in science
Just as in philosophy, the scientific concept of fact is central to fundamental questions regarding the nature, methods, scope and validity of scientific reasoning.
In the most basic sense, a scientific fact is an objective and verifiable observation; in contrast with a conjecture or theory, which is intended to explain or interpret facts.
Various scholars have offered significant refinements to this basic formulation, some of which are detailed below. Also, rigorous scientific use of the term "fact" is careful to distinguish: 1) states of affairs in the external world; from 2) assertions of fact that may be considered relevant in scientific analysis. The term is used in both senses in the philosophy of science.
The fact-value distinction
Moral philosophers since David Hume have debated whether values are objective, and thus factual. In A Treatise of Human Nature Hume pointed out that there is no obvious way for a series of statements about what ought to be the case to be derived from a series of statements of what is the case. Those who insist that there is a logical gulf between facts and values, such that it is fallacious to attempt to derive values from facts, include G. E. Moore, who called attempting to do so the Naturalistic Fallacy.
The fetish of factualized truth, fossilized truth, the iron band of so-called unchanging truth, holds one blindly in a closed circle of cold fact. One can be technically right as to fact and everlastingly wrong in the truth.