Fact–value distinction
The fact–value distinction is a fundamental epistemological distinction described between:

 Statements of fact (positive or descriptive statements), based upon reason and physical observation, and which are examined via the empirical method. Statements of value (normative or prescriptive statements), which encompass ethics and aesthetics, and are studied via axiology. This barrier between fact and value, as construed in epistemology, implies it is impossible to derive ethical claims from factual arguments, or to defend the former using the latter. The fact–value distinction is closely related to, and derived from, the is–ought problem in moral philosophy, characterized by David Hume. Religion and science 

In his essay Science as a Vocation (1917) Max Weber draws a distinction between facts and values. He argues that facts can be determined through the methods of a value-free, objective social science, while values are derived through culture and religion, the truth of which cannot be known through science. He writes, "it is one thing to state facts, to determine mathematical or logical relations or the internal structure of cultural values, while it is another thing to answer questions of the value of culture and its individual contents and the question of how one should act in the cultural community and in political associations. These are quite heterogeneous problems." In his 1919 essay Politics as a Vocation, he argues that facts, like actions, do not in themselves contain any intrinsic meaning or power: "any ethic in the world could establish substantially identical commandments applicable to all relationships." To MLK Jr., "Science deals mainly with facts; religion deals mainly with values. The two are not rivals. They are complementary." He stated that science keeps religion from"crippling irrationalism and paralyzing obscurantism" whereas Religion prevents science from "falling into ... obsolete materialism and moral nihilism." Albert Einstein remarked that

David Hume's skepticism

In A Treatise of Human Nature (1739), David Hume discusses the problems in grounding normative statements in positive statements, that is in deriving ought from is. It is generally regarded that Hume considered such derivations untenable, and his 'is–ought' problem is considered a principal question of moral philosophy. Hume shared a political viewpoint with early Enlightenment philosophers such as Thomas Hobbes (1588–1679) and John Locke (1632–1704). Specifically, Hume, at least to some extent, argued that religious and national hostilities that divided European society were based on unfounded beliefs. In effect, Hume contended that such hostilities are not found in nature, but are a human creation, depending on a particular time and place, and thus unworthy of mortal conflict. Prior to Hume, Aristotelian philosophy maintained that all actions and causes were to be interpreted teleologically. This rendered all facts about human action examinable under a normative framework defined by cardinal virtues and capital vices. "Fact" in this sense was not value-free, and the fact-value distinction was an alien concept. The decline of Aristotelianism in the 16th century set the framework in which those theories of knowledge could be revised. Naturalistic fallacy

The fact–value distinction is closely related to the naturalistic fallacy, a topic debated in ethical and moral philosophy. G. E. Moore believed it essential to all ethical thinking. However, contemporary philosophers like Philippa Foot have called into question the validity of such assumptions. Others, such as Ruth Anna Putnam, argue that even the most "scientific" of disciplines are affected by the "values" of those who research and practice the vocation. Nevertheless, the difference between the naturalistic fallacy and the fact–value distinction is derived from the manner in which modern social science has used the fact–value distinction, and not the strict naturalistic fallacy to articulate new fields of study and create academic disciplines. Moralistic fallacy
The fact–value distinction is also closely related to the moralistic fallacy, an invalid inference of factual conclusions from purely evaluative premises. For example, an invalid inference "Because everybody ought to be equal, there are no innate genetic differences between people" is an instance of the moralistic fallacy. As for the naturalistic fallacy one attempts to move from an "is" to an "ought" statement, with the moralistic fallacy one attempts to move from an "ought" to an "is" statement. Nietzsche's table of values
Friedrich Nietzsche (1844–1900) in Thus Spoke Zarathustra said that a table of values hangs above every great people. Nietzsche argues that what is common among different peoples is the act of esteeming, of creating values, even if the values are different from one people to the next. Nietzsche asserts that what made people great was not the content of their beliefs, but the act of valuing. Thus the values a community strives to articulate are not as important as the collective will to act on those values. The willing is more essential than the intrinsic worth of the goal itself, according to Nietzsche. "A thousand goals have there been so far," says Zarathustra, "for there are a thousand peoples. Only the yoke for the thousand necks is still lacking: the one goal is lacking. Humanity still has no goal." Hence, the title of the aphorism, "On The Thousand And One Goals." The idea that one value-system is no more worthy than the next, although it may not be directly ascribed to Nietzsche, has become a common premise in modern social science. Max Weber and Martin Heidegger absorbed it and made it their own. It shaped their philosophical endeavor, as well as their political understanding. Criticisms
Virtually all modern philosophers affirm some sort of fact–value distinction, insofar as they distinguish between science and "valued" disciplines such as ethics, aesthetics, or the fine arts. However, philosophers such as Hilary Putnam argue that the distinction between fact and value is not as absolute as Hume envisioned. Philosophical pragmatists, for instance, believe that true propositions are those that are useful or effective in predicting future (empirical) states of affairs. Far from being value-free, the pragmatists' conception of truth or facts directly relates to an end (namely, empirical predictability) that human beings regard as normatively desirable. Other thinkers, such as N. Hanson among others, talk of theory-ladenness, and reject an absolutist fact–value distinction by contending that our senses are imbued with prior conceptualizations, making it impossible to have any observation that is totally value-free, which is how Hume and the later positivists conceived of facts. Functionalist counterexamples
Several counterexamples have been offered by philosophers claiming to show that there are cases when an evaluative statement does indeed logically follow from a factual statement. A. N. Prior argues, from the statement "He is a sea captain," that it logically follows, "He ought to do what a sea captain ought to do." Alasdair MacIntyre argues, from the statement "This watch is grossly inaccurate and irregular in time-keeping and too heavy to carry about comfortably," that the evaluative conclusion validly follows, "This is a bad watch." John Searle argues, from the statement "Jones promised to pay Smith five dollars," that it logically follows that "Jones ought to pay Smith five dollars", such that the act of promising by definition places the promiser under obligation. Moral realism
Philippa Foot adopts a moral realist position, criticizing the idea that when evaluation is superposed on fact there has been a "committal in a new dimension". She introduces, by analogy, the practical implications of using the word "injury". Not just anything counts as an injury. There must be some impairment. When we suppose a man wants the things the injury prevents him from obtaining, haven’t we fallen into the old naturalist fallacy? Foot argues that the virtues, like hands and eyes in the analogy, play so large a part in so many operations that it is implausible to suppose that a committal in a non-naturalist dimension is necessary to demonstrate their goodness. Of Weber 
Philosopher Leo Strauss criticizes Weber for attempting to isolate reason completely from opinion. Strauss acknowledges the philosophical trouble of deriving "ought" from "is", but argues that what Weber has done in his framing of this puzzle is in fact deny altogether that the "ought" is within reach of human reason. Strauss worries that if Weber is right, we are left with a world in which the knowable truth is a truth that cannot be evaluated according to ethical standards. This conflict between ethics and politics would mean that there can be no grounding for any valuation of the good, and without reference to values, facts lose their meaning. See also

 Baden School
 Empiricism
 Is–ought problem
 Non-overlapping magisteria
 Relativism

References

Bibliography
 Hume, David. A Treatise of Human Nature. 1739–1740
 Hume, David. An Enquiry Concerning Human Understanding. 1748
 Nietzsche, Friedrich. Thus Spoke Zarathustra. 1883–1891. Translated by R.J. Hollingdale. New York: Penguin, 1969
 
 Silvestri P. (ed. ), L. Einaudi, On Abstract and Historical Hypotheses and on Value judgments in Economic Sciences, Critical edition with an Introduction and Afterword by Paolo Silvestri, Routledge, London & New York, 2017. Concepts in epistemology
Belief
Conceptual distinctions
Value (ethics)
Religion and science
Concepts in aesthetics