Open-question argument
The open-question argument is a philosophical argument put forward by British philosopher G. E. Moore in of Principia Ethica, to refute the equating of the property of goodness with some non-moral property, X, whether natural or supernatural. That is, Moore's argument attempts to show that no moral property is identical to a natural property. The argument takes the form of a syllogism modus tollens:
The type of question Moore refers to in this argument is an identity question, "Is it true that X is Y?" Such a question is an open question if a conceptually competent speaker can question this; otherwise it is closed. For example, "I know he is a vegan, but does he eat meat?" would be a closed question. However, "I know that it is pleasurable, but is it good?" is an open question; the answer cannot be derived from the meaning of the terms alone.
The open-question argument claims that any attempt to identify morality with some set of observable, natural properties will always be liable to an open question, and that if this is true, then moral facts cannot be reduced to natural properties and that therefore ethical naturalism is false. Put another way, Moore is saying that any attempt to define good in terms of a natural property fails because such definitions can be transformed into closed questions ; however, all purported naturalistic definitions of good are transformable into open questions, for it can still be questioned whether good is the same thing as pleasure, etc. Shortly before, Moore had said if good is defined as pleasure, or any other natural property, "good" may be substituted for "pleasure", or that other property, anywhere where it occurs. However, "pleasure is good" is a meaningful, informative statement; but "good is good" is an uninformative tautology.
Objections and rejoinders
Begging the question
The idea that Moore begs the question was first raised by W. Frankena. Since analytic equivalency, for two objects X and Y, logically results in the question "Is it true that X is Y?" being meaningless, to say that the question is meaningless is to concede analytic equivalency. Thus Moore begs the question in the second premise. He assumes that the question is a meaningful one. This begs the question and the open-question argument thus fails.In response to this, the open-question argument can be reformulated. The Darwall-Gibbard-Railton reformulation argues for the impossibility of equating a moral property with a non-moral one using the internalist theory of motivation.
This evidently presupposes the internalist theory of motivation, in contrast to the externalist theory of motivation, also known as the Humean theory of motivation. If internalism is true, then the OQA avoids begging the question against the naturalist, and succeeds in showing that the good cannot be equated to some other property.
The argument is also contested on the grounds of the supremacy of internalism. Internalism is supported by the belief–desire–intention model of motivation, whereby desire and belief combine to form intention, and thereby, action. To argue for the special motivational effects of moral beliefs is to commit the fallacy of special pleading.
Meaningful analysis
The main assumption within the open-question argument can be found within premise 1. It is assumed that analytic equivalency will result in meaningless analysis. Thus, if we understand Concept C, and Concept C* can be analysed in terms of Concept C, then we should grasp concept C* by virtue of our understanding of Concept C. Yet it is obvious that such understanding of Concept C* only comes about through the analysis proper. Mathematics would be the prime example: mathematics is tautological and its claims are true by definition, yet we can develop new mathematical conceptions and theorems. Thus, X might well be analytically equivalent to the good, and still the question of "Is X good?" can be meaningful. Ergo premise 1 does not hold and the argument falls.Frege sense–reference distinction
Sense and reference are two different aspects of some terms' meanings. A term's reference is the object to which the term refers, while the term's sense is the way that the term refers to that object.There is a difference between the sense of a term and its reference. Thus, we can understand a claim like "goodness is identical with pleasure" as an a posteriori identity claim similar to "Water is H2O". The question "This is H2O but is it water?" is intelligible and so, in that limited sense, whether or not water is H2O is an open question; note that this does not address the issue of significance. But that does not lead us to conclude that water is not H2O. "Water is H2O" is an identity claim that is known to be true a posteriori. Another example is "redness" being identical to certain phenomena of electromagnetism. This is discovered by empirical investigation. Similarly, many moral naturalists argue that "rightness" can be discovered as an a posteriori truth, by investigating the different claims, like that of pleasure being the good, or of duty being the good.
This is done by invoking rightness and wrongness to explain certain empirical phenomena, and then discovering a posteriori whether maximizing utility occupies the relevant explanatory role. For example, they argue that since right actions contingently have certain effects e.g. being causally responsible for a tendency towards social stability—so it follows we can fix the term "right" refer to the empirical description "the property of acts, whatever it is, that is causally responsible for their tendency towards social stability." With this description for "right," we can then investigate which acts accomplish this: e.g. those actions that maximize utility. We can then conclude that we have learned that "right" refers to "maximizing utility" through a posteriori means.
The Frege sense–reference distinction can be understood in layman's terms by using the analogy of the Masked Man. A citizen living on the frontiers of the Wild West is told by the sheriff that his brother is the Masked Man who has recently been robbing banks. The citizen protests that he understands who his brother is, and who the Masked Man is supposed to be, and can meaningfully ask, "Is my brother the Masked Man?" Obviously, analytic equivalency is of no relevance here. The matter is an empirical one, which the citizen must investigate a posteriori. The absurdity of dismissing the claim as such is apparent.
However, the above account of a sort of a posteriori moral search is unsatisfactory in that normal value, and not moral value, can be used to explain the relevant events. Normal value arises from the relationship between desire and a state of affairs. People tend also to objectify such value, into categorical moral value, though this is fallacious. So, a situation that can be explained by the existence of real moral value can also be explained by non-moral value. This explanation is far simpler, given the ontological difficulties surrounding moral value. As J. L. Mackie argued with his argument from queerness, moral values that exist in the natural world, is highly queer, and we ought to favour a completely naturalistic explanation instead.
Another problem with the a posteriori moral search is that we lack an epistemic account of how we access moral facts. This is the epistemic aspect of Mackie's argument from queerness. Failing such an account, the postulation of moral value will be egregious.