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 discusses the problem in book III, part I, section I of his book, A Treatise of Human Nature (1739): In every system of morality, which I have hitherto met with, I have always remarked, that the author proceeds for some time in the ordinary way of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when of a sudden I am surprised to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not.

But as authors do not commonly use this precaution, I shall presume to recommend it to the readers; and am persuaded, that this small attention would subvert all the vulgar systems of morality, and let us see, that the distinction of vice and virtue is not founded merely on the relations of objects, nor is perceived by reason.

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.

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.

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.

[citation needed] 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.

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.

Although many scientists do recognize teleonomy (a tendency in nature), few philosophers appeal to it (this time, to avoid the naturalistic fallacy).

Alasdair MacIntyre himself suggests that a person's purpose comes from their culture, making him a sort of ethical relativist.

[16] To some, this may immediately suggest the question: "How can we know what is a right desire if it is already admitted that it is not based on the more actual reality of things independent of the mind?"

Thus, right desire cannot be defined properly, but a way to refer to its meaning may be found through a self-evident prescriptive truth.

The terms "real good" and "right desire" cannot be defined apart from each other, and thus their definitions would contain some degree of circularity, but the stated self-evident truth indicates a meaning particular to the ideas sought to be understood, and it is (the moral cognitivist might claim) impossible to think the opposite without a contradiction.

First of all, Hilary Putnam, by tracing back the quarrel to Hume's dictum, claims fact/value entanglement as an objection, since the distinction between them entails a value.

[21] 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.

But we should look carefully at the crucial move in that argument, and query the suggestion that someone might happen not to want anything for which he would need the use of hands or eyes.

[23]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.

Philosophers who have supposed that actual action was required if "good" were to be used in a sincere evaluation have got into difficulties over weakness of will, and they should surely agree that enough has been done if we can show that any man has reason to aim at virtue and avoid vice.

[24]Hilary Putnam argues that philosophers who accept Hume's "is–ought" distinction reject his reasons in making it, and thus undermine the entire claim.