Is–ought problem
The is–ought problem, as articulated by the Scottish philosopher and historian David Hume, arises when one makes claims about what ought to be that are based solely on statements about what is. Hume found that there seems to be a significant difference between descriptive statements and prescriptive statements, and that it is not obvious how one can coherently transition from descriptive statements to prescriptive ones.
Hume's law or Hume's guillotine is the thesis that an ethical or judgmental conclusion cannot be inferred from purely descriptive factual statements.
A similar view is defended by G. E. Moore's open-question argument, intended to refute any identification of moral properties with natural properties, which is asserted by ethical naturalists, who do not deem the naturalistic fallacy a fallacy.
The is–ought problem is closely related to the fact–value distinction in epistemology. Though the terms are often used interchangeably, academic discourse concerning the latter may encompass aesthetics in addition to ethics.
Overview
Hume discusses the problem in book III, part I, section I of his book, A Treatise of Human Nature :Hume calls for caution against such inferences in the absence of any explanation of how the ought-statements follow from the is-statements. But how exactly can an "ought" be derived from an "is"? The question, prompted by Hume's small paragraph, has become one of the central questions of ethical theory, and Hume is usually assigned the position that such a derivation is impossible.
In modern times, "Hume's law" often denotes the informal thesis that, if a reasoner only has access to non-moral factual premises, the reasoner cannot logically infer the truth of moral statements; or, more broadly, that one cannot infer evaluative statements from non-evaluative statements. An alternative definition of Hume's law is that "If P implies Q, and Q is moral, then P is moral". This interpretation-driven definition avoids a loophole with the principle of explosion. Other versions state that the is–ought gap can technically be formally bridged without a moral premise, but only in ways that are formally "vacuous" or "irrelevant", and that provide no "guidance". For example, one can infer from "The Sun is yellow" that "Either the Sun is yellow, or it is wrong to murder". But this provides no relevant moral guidance; absent a contradiction, one cannot deductively infer that "it is wrong to murder" solely from non-moral premises alone, adherents argue.
Implications
The apparent gap between "is" statements and "ought" statements, when combined with Hume's fork, renders "ought" statements of dubious validity. Hume's fork is the idea that all items of knowledge are based either on logic and definitions, or else on observation. If the is–ought problem holds, then "ought" statements do not seem to be known in either of these two ways, and it would seem that there can be no moral knowledge. Moral skepticism and non-cognitivism work with such conclusions.Responses
Oughts and goals
contend that moral truths exist, and that their truth value relates to facts about physical reality. Many modern naturalistic philosophers see no impenetrable barrier in deriving "ought" from "is", believing it can be done whenever we analyze goal-directed behavior. They suggest that a statement of the form "In order for agent A'' to achieve goal B, A reasonably ought to do C"'' exhibits no category error and may be factually verified or refuted. "Oughts" exist, then, in light of the existence of goals. A counterargument to this response is that it merely pushes back the "ought" to the subjectively valued "goal" and thus provides no fundamentally objective basis to one's goals which, consequentially, provides no basis of distinguishing moral value of fundamentally different goals. A dialectical naturalist response to this objection is that although it is true that individual goals have a degree of subjectivity, the process through which the existence of goals is made possible is not subjective—that is, the advent of organisms capable of subjectivity, having occurred through the objective process of evolution. This dialectical approach goes further to state that subjectivity should be conceptualized as objectivity at its highest point, having been the result of an unfolding developmental process.This is similar to work done by the moral philosopher Alasdair MacIntyre, who attempts to show that because ethical language developed in the West in the context of a belief in a human telos—an end or goal—our inherited moral language, including terms such as good and bad, have functioned, and function, to evaluate the way in which certain behaviors facilitate the achievement of that telos. In an evaluative capacity, therefore, good and bad carry moral weight without committing a category error. For instance, a pair of scissors that cannot easily cut through paper can legitimately be called bad since it cannot fulfill its purpose effectively. Likewise, if a person is understood as having a particular purpose, then behaviour can be evaluated as good or bad in reference to that purpose. In plainer words, a person is acting good when that person fulfills that person's purpose.
Even if the concept of an "ought" is meaningful, this need not involve morality. This is because some goals may be morally neutral, or against what is moral. A poisoner might realize his victim has not died and say, for example, "I ought to have used more poison," since his goal is to murder. The next challenge of a moral realist is thus to explain what is meant by a "moral ought".
Discourse ethics
Proponents of discourse ethics argue that the very act of discourse implies certain "oughts", that is, certain presuppositions that are necessarily accepted by the participants in discourse, and can be used to further derive prescriptive statements. They therefore argue that it is incoherent to argumentatively advance an ethical position on the basis of the is–ought problem, which contradicts these implied assumptions.Moral oughts
As MacIntyre explained, someone may be called a good person if people have an inherent purpose. Many ethical systems appeal to such a purpose. This is true of some forms of moral realism, which states that something can be wrong, even if every thinking person believes otherwise. The ethical realist might suggest that humans were created for a purpose, especially if they are an ethical non-naturalist. If the ethical realist is instead an ethical naturalist, they may start with the fact that humans have evolved and pursue some sort of evolutionary ethics.Not all moral systems appeal to a human telos or purpose. This is because it is not obvious that people even have any sort of natural purpose, or what that purpose would be. Although many scientists do recognize teleonomy, few philosophers appeal to it.
Goal-dependent oughts run into problems even without an appeal to an innate human purpose. Consider cases where one has no desire to be good—whatever it is. If, for instance, a person wants to be good, and good means washing one's hands, then it seems one morally ought to wash their hands. The bigger problem in moral philosophy is what happens if someone does not want to be good, whatever its origins? Put simply, in what sense ought we to hold the goal of being good? It seems one can ask "how am I rationally required to hold 'good' as a value, or to pursue it?"
The issue above mentioned is a result of an important ethical relativist critique. Even if "oughts" depend on goals, the ought seems to vary with the person's goal. This is the conclusion of the ethical subjectivist, who says a person can only be called good according to whether they fulfill their own, self-assigned goal. Alasdair MacIntyre himself suggests that a person's purpose comes from their culture, making him a sort of ethical relativist. Ethical relativists acknowledge local, institutional facts about what is right, but these are facts that can still vary by society. Thus, without an objective "moral goal", a moral ought is difficult to establish. G. E. M. Anscombe was particularly critical of the word "ought" for this reason; understood as "We need such-and-such, and will only get it this way"for somebody may need something immoral, or else find that their noble need requires immoral action. Anscombe would even go as far to suggest that "the concepts of obligation, and dutymoral obligation and moral duty, that is to sayand of what is morally right and wrong, and of the moral sense of 'ought,' ought to be jettisoned if this is psychologically possible".
If moral goals depend on private assumptions or public agreement, so may morality as a whole. For example, Canada might call it good to maximize global welfare, where a citizen, Alice, calls it good to focus on herself, and then her family, and finally her friends. It does not seem that Alice can be objectively or rationally bound—without regard to her personal values nor those of groups of other people—to act a certain way. In other words, we may not be able to say "You just should do this". Moreover, persuading her to help strangers would necessarily mean appealing to values she already possesses. This is another interest of normative ethics—questions of binding forces.
There may be responses to the above relativistic critiques. As mentioned above, ethical realists that are non-natural can appeal to God's purpose for humankind. On the other hand, naturalistic thinkers may posit that valuing people's well-being is the purpose of ethics, or else the only relevant purpose worth talking about. This is the move made by natural law, scientific moralists and some utilitarians.