Moral skepticism (or moral scepticism) is a class of metaethical theories all members of which entail that no one has any moral knowledge. Many moral skeptics also make the stronger, modal claim that moral knowledge is impossible. Moral skepticism is particularly opposed to moral realism: the view that there are knowable and objective moral truths.
Some defenders of moral skepticism include Pyrrho, Aenesidemus, Sextus Empiricus, David Hume, J. L. Mackie (1977), Max Stirner, Friedrich Nietzsche, Richard Joyce (2001), Michael Ruse, Joshua Greene, Richard Garner, Walter Sinnott-Armstrong (2006b), and the psychologist James Flynn. Strictly speaking, Gilbert Harman (1975) argues in favor of a kind of moral relativism, not moral skepticism. However, he has influenced some contemporary moral skeptics.
Moral skepticism divides into three subclasses: moral error theory (or moral nihilism), epistemological moral skepticism, and noncognitivism. All three of these theories share the same conclusions, which are:
However, each method arrives at (a) and (b) by different routes.
Moral error theory holds that we do not know that any moral claim is true because
Epistemological moral skepticism is a subclass of theory, the members of which include Pyrrhonian moral skepticism and dogmatic moral skepticism. All members of epistemological moral skepticism share two things: first, they acknowledge that we are unjustified in believing any moral claim, and second, they are agnostic on whether (i) is true (i.e. on whether all moral claims are false).
Finally, Noncognitivism holds that we can never know that any moral claim is true because moral claims are incapable of being true or false (they are not truth-apt). Instead, moral claims are imperatives (e.g. "Don't steal babies!"), expressions of emotion (e.g. "stealing babies: Boo!"), or expressions of "pro-attitudes" ("I do not believe that babies should be stolen.")
Moral error theory is a position characterized by its commitment to two propositions: (i) all moral claims are false and (ii) we have reason to believe that all moral claims are false. The most famous moral error theorist is J. L. Mackie, who defended the metaethical view in Ethics: Inventing Right and Wrong (1977). Mackie has been interpreted as giving two arguments for moral error theory.
The first argument people attribute to Mackie, often called the argument from queerness, holds that moral claims imply motivation internalism (the doctrine that "It is necessary and a priori that any agent who judges that one of his available actions is morally obligatory will have some (defeasible) motivation to perform that action"). Because motivation internalism is false, however, so too are all moral claims.
The other argument often attributed to Mackie, often called the argument from disagreement, maintains that any moral claim (e.g. "Killing babies is wrong") entails a correspondent "reasons claim" ("one has reason not to kill babies"). Put another way, if "killing babies is wrong" is true then everybody has a reason to not kill babies. This includes the psychopath who takes great pleasure from killing babies, and is utterly miserable when he does not have their blood on his hands. But, surely, (if we assume that he will suffer no reprisals) this psychopath has every reason to kill babies, and no reason not to do so. All moral claims are thus false.
All versions of epistemological moral skepticism hold that we are unjustified in believing any moral proposition. However, in contradistinction to moral error theory, epistemological moral skeptical arguments for this conclusion do not include the premise that "all moral claims are false." For example, Michael Ruse gives what Richard Joyce calls an "evolutionary argument" for the conclusion that we are unjustified in believing any moral proposition. He argues that we have evolved to believe moral propositions because our believing the same enhances our genetic fitness (makes it more likely that we will reproduce successfully). However, our believing these propositions would enhance our fitness even if they were all false (they would make us more cooperative, etc.). Thus, our moral beliefs are unresponsive to evidence; they are analogous to the beliefs of a paranoiac. As a paranoiac is plainly unjustified in believing his conspiracy theories, so too are we unjustified in believing moral propositions. We therefore have reason to jettison our moral beliefs.
There are two different opinions that may follow from moral skepticism.
Amoralism is the idea that we should abandon morality.
Criticisms of moral skepticism come primarily from moral realists. The moral realist argues that there is in fact good reason to believe that there are objective moral truths and that we are justified in holding many moral beliefs. One moral realist response to moral error theory holds that it "proves too much"—if moral claims are false because they entail that we have reasons to do certain things regardless of our preferences, then so too are "hypothetical imperatives" (e.g. "if you want to get your hair-cut you ought to go to the barber"). This is because all hypothetical imperatives imply that "we have reason to do that which will enable us to accomplish our ends" and so, like moral claims, they imply that we have reason to do something regardless of our preferences.
If moral claims are false because they have this implication, then so too are hypothetical imperatives. But hypothetical imperatives are true. Thus the argument from the non-instantiation of (what Mackie terms) "objective prescriptivity" for moral error theory fails. Russ Shafer-Landau and Daniel Callcut have each outlined anti-skeptical strategies. Callcut argues that moral skepticism should be scrutinized in introductory ethics classes in order to get across the point that "if all views about morality, including the skeptical ones, face difficulties, then adopting a skeptical position is not an escape from difficulty." 
Anita Superson is a Professor of Philosophy at the University of Kentucky. She was also the visiting Churchill Humphrey and Alex P. Humphrey Professor of Feminist Philosophy at the University of Waterloo during the winter term of 2013.Ethical naturalism
Ethical naturalism (also called moral naturalism or naturalistic cognitivistic definism) is the meta-ethical view which claims that:
Ethical sentences express propositions.
Some such propositions are true.
Those propositions are made true by objective features of the world, independent of human opinion.
These moral features of the world are reducible to some set of non-moral featuresEthics
Ethics or moral philosophy is a branch of philosophy that involves systematizing, defending, and recommending concepts of right and wrong conduct. The field of ethics, along with aesthetics, concerns matters of value, and thus comprises the branch of philosophy called axiology.Ethics seeks to resolve questions of human morality by defining concepts such as good and evil, right and wrong, virtue and vice, justice and crime. As a field of intellectual inquiry, moral philosophy also is related to the fields of moral psychology, descriptive ethics, and value theory.
Three major areas of study within ethics recognized today are:
Meta-ethics, concerning the theoretical meaning and reference of moral propositions, and how their truth values (if any) can be determined
Normative ethics, concerning the practical means of determining a moral course of action
Applied ethics, concerning what a person is obligated (or permitted) to do in a specific situation or a particular domain of actionEvolutionary ethics
Evolutionary ethics is a field of inquiry that explores how evolutionary theory might bear on our understanding of ethics or morality. The range of issues investigated by evolutionary ethics is quite broad. Supporters of evolutionary ethics have claimed that it has important implications in the fields of descriptive ethics, normative ethics, and metaethics.
Descriptive evolutionary ethics consists of biological approaches to morality based on the alleged role of evolution in shaping human psychology and behavior. Such approaches may be based in scientific fields such as evolutionary psychology, sociobiology, or ethology, and seek to explain certain human moral behaviors, capacities, and tendencies in evolutionary terms. For example, the nearly universal belief that incest is morally wrong might be explained as an evolutionary adaptation that furthered human survival.
Normative (or prescriptive) evolutionary ethics, by contrast, seeks not to explain moral behavior, but to justify or debunk certain normative ethical theories or claims. For instance, some proponents of normative evolutionary ethics have argued that evolutionary theory undermines certain widely held views of humans' moral superiority over other animals.
Evolutionary metaethics asks how evolutionary theory bears on theories of ethical discourse, the question of whether objective moral values exist, and the possibility of objective moral knowledge. For example, some evolutionary ethicists have appealed to evolutionary theory to defend various forms of moral anti-realism (the claim, roughly, that objective moral facts do not exist) and moral skepticism.Gilbert Harman
Gilbert Harman (born 26 May 1938) is an American philosopher, who taught at Princeton University from 1963 until his retirement in 2017. He has published widely in philosophy of language, cognitive science, philosophy of mind, ethics, moral psychology, epistemology, statistical learning theory, and metaphysics. He and George Miller co-directed the Princeton University Cognitive Science Laboratory. Harman has taught or co-taught courses in Electrical Engineering, Computer Science, Psychology, Philosophy, and Linguistics.Index of ethics articles
This Index of ethics articles puts articles relevant to well-known ethical (right and wrong, good and bad) debates and decisions in one place - including practical problems long known in philosophy, and the more abstract subjects in law, politics, and some professions and sciences. It lists also those core concepts essential to understanding ethics as applied in various religions, some movements derived from religions, and religions discussed as if they were a theory of ethics making no special claim to divine status.List of philosophies
Philosophical schools of thought and philosophical movements.Local skepticism
Local skepticism is the view that one cannot possess knowledge in some particular domain. It contrasts with global skepticism (also known as absolute skepticism or universal skepticism), the view that one cannot know anything at all.Meta-ethics
Meta-ethics is the branch of ethics that seeks to understand the nature of ethical properties, statements, attitudes, and judgments. Meta-ethics is one of the three branches of ethics generally studied by philosophers, the others being normative ethics and applied ethics.
While normative ethics addresses such questions as "What should I do?", evaluating specific practices and principles of action, meta-ethics addresses questions such as "What is goodness?" and "How can we tell what is good from what is bad?", seeking to understand the nature of ethical properties and evaluations.
Some theorists argue that a metaphysical account of morality is necessary for the proper evaluation of actual moral theories and for making practical moral decisions; others reason from opposite premises and suggest that studying moral judgments about proper actions can guide us to a true account of the nature of morality.Moral nihilism
Moral nihilism (also known as ethical nihilism) is the meta-ethical view that nothing is morally right or wrong.
Moral nihilism is distinct from moral relativism, which allows for actions wrong relative to a particular culture or individual. It is also distinct from expressivism, according to which when we make moral claims, "We are not making an effort to describe the way the world is ... we are venting our emotions, commanding others to act in certain ways, or revealing a plan of action" (Shafer-Landau 2010, pp. 292–293).
Nihilism does not imply that we should give up using moral or ethical language; some nihilists contend that it remains a useful tool.Moral realism
Moral realism (also ethical realism or moral Platonism) is the position that ethical sentences express propositions that refer to objective features of the world (that is, features independent of subjective opinion), some of which may be true to the extent that they report those features accurately. This makes moral realism a non-nihilist form of ethical cognitivism (which accepts that ethical sentences express propositions and can therefore be evaluated as true or false) with an ontological orientation, standing in opposition to all forms of moral anti-realism and moral skepticism, including ethical subjectivism (which denies that moral propositions refer to objective facts), error theory (which denies that any moral propositions are true); and non-cognitivism (which denies that moral sentences express propositions at all). Within moral realism, the two main subdivisions are ethical naturalism and ethical non-naturalism.
Many philosophers claim that moral realism may be dated back at least to Plato as a philosophical doctrine,
and that it is a fully defensible form of moral doctrine. A survey from 2009 involving 3,226 respondents found that 56% of philosophers accept or lean towards moral realism (28%: anti-realism; 16%: other). Some notable examples of robust moral realists include David Brink, John McDowell, Peter Railton, Geoffrey Sayre-McCord, Michael Smith, Terence Cuneo, Russ Shafer-Landau, G. E. Moore, John Finnis, Richard Boyd, Nicholas Sturgeon, Thomas Nagel and Derek Parfit. Norman Geras has argued that Karl Marx was a moral realist. Moral realism has been studied in the various philosophical and practical applications.Oliver Wendell Holmes Jr.
Oliver Wendell Holmes Jr. (March 8, 1841 – March 6, 1935) was an American jurist who served as an Associate Justice of the Supreme Court of the United States from 1902 to 1932, and as Acting Chief Justice of the United States in January–February 1930. Noted for his long service, concise and pithy opinions, and deference to the decisions of elected legislatures, he is one of the most widely cited United States Supreme Court justices in history, particularly for his "clear and present danger" opinion for a unanimous Court in the 1919 case of Schenck v. United States, and is one of the most influential American common law judges, honored during his lifetime in Great Britain as well as the United States. Holmes retired from the court at the age of 90, making him the oldest justice in the Supreme Court's history. He also served as an Associate Justice and as Chief Justice of the Massachusetts Supreme Judicial Court, and was Weld Professor of Law at his alma mater, Harvard Law School.
Profoundly influenced by his experience fighting in the American Civil War, Holmes helped move American legal thinking towards legal realism, as summed up in his maxim: "The life of the law has not been logic; it has been experience." Holmes espoused a form of moral skepticism and opposed the doctrine of natural law, marking a significant shift in American jurisprudence. In one of his most famous opinions, his dissent in Abrams v. United States (1919), he regarded the United States Constitution as "an experiment, as all life is an experiment" and believed that as a consequence "we should be eternally vigilant against attempts to check the expression of opinions that we loathe and believe to be fraught with death." During his tenure on the Supreme Court, to which he was appointed by President Theodore Roosevelt, he supported efforts for economic regulation and advocated broad freedom of speech under the First Amendment. These positions as well as his distinctive personality and writing style made him a popular figure, especially with American progressives. His jurisprudence influenced much subsequent American legal thinking, including judicial consensus supporting New Deal regulatory law, and influential schools of pragmatism, critical legal studies, and law and economics. He was one of only a handful of justices to be known as a scholar; The Journal of Legal Studies has identified Holmes as the third-most cited American legal scholar of the 20th century.Perspectivism
Perspectivism (German: Perspektivismus) is the view that perception, experience, and reason change according to the viewer's relative perspective and interpretation.There are many possible conceptual schemes, or perspectives in which judgment of truth or value can be made. This is often taken to imply that no way of seeing the world can be taken as definitively "true", but does not necessarily entail that all perspectives are equally valid. Leibniz integrated this view into his philosophy, but Nietzsche fully developed it.It rejects both the idea of perspective-free or interpretation-free objective reality.Psychological determinism
Daniel Bader discusses two forms of psychological determinism:
Orectic psychological determinism is the view that we always act upon our greatest drive. This is often called psychological hedonism, and if the drive is specified for self-interest: psychological egoism.
Rational psychological determinism claims that we always act according to our "strongest" or "best" reason.Richard Joyce (philosopher)
Richard Joyce (born 1966) is a British-Australian-New Zealand philosopher, known for his contributions to the fields of meta-ethics and moral psychology. He is Professor of Philosophy at Victoria University of Wellington.Skepticism
Skepticism (American English) or scepticism (British English, Australian English, and Canadian English) is generally a questioning attitude or doubt towards one or more items of putative knowledge or belief or dogma. It is often directed at domains, such as the supernatural, morality (moral skepticism), theism (skepticism about the existence of God), or knowledge (skepticism about the possibility of knowledge, or of certainty). Formally, skepticism as a topic occurs in the context of philosophy, particularly epistemology, although it can be applied to any topic such as politics, religion, and pseudoscience.
Philosophical skepticism comes in various forms. Radical forms of skepticism deny that knowledge or rational belief is possible and urge us to suspend judgment on many or all controversial matters. More moderate forms of skepticism claim only that nothing can be known with certainty, or that we can know little or nothing about the big question in life, such as whether God exists or whether there is an afterlife. Religious skepticism is "doubt concerning basic religious principles (such as immortality, providence, and revelation)". Scientific skepticism concerns testing beliefs for reliability, by subjecting them to systematic investigation using the scientific method, to discover empirical evidence for them.The Contemporary Review
The Contemporary Review is a British biannual, formerly quarterly, magazine. It has an uncertain future as of 2013.Value pluralism
In ethics, value pluralism (also known as ethical pluralism or moral pluralism) is the idea that there are several values which may be equally correct and fundamental, and yet in conflict with each other. In addition, value-pluralism postulates that in many cases, such incompatible values may be incommensurable, in the sense that there is no objective ordering of them in terms of importance. Value pluralism is opposed to value monism.
Value-pluralism is a theory in metaethics, rather than a theory of normative ethics, or a set of values in itself. Oxford philosopher and historian of ideas Isaiah Berlin is credited with being the first to popularize a substantial work describing the theory of objective value-pluralism, bringing it to the attention of academia (cf. the Isaiah Berlin Virtual Library). The related idea that fundamental values can and, in some cases, do conflict with each other is prominent in the thought of Max Weber, captured in his notion of "polytheism".