In the previous two clips, we've seen that views in normative ethics are susceptible to falsification. Evaluative thought experiments that function as counterexamples to the target view. That comes as no surprise since in philosophy there are no crucial thought experiments that settle a question once and for all. However, in ethics and moral philosophy, there is also an extra reason why arguments are indecisive, and why views remain very much up in the air. The famous and infamous gap between is and ought, that Hume already touched on. It's one thing to identify the action that produces the greatest happiness for the greatest number, it's quite another thing to say that happiness is good and that as a result, the action is right. In this clip, we'll discuss how more upgrades Hume's gap. To situate more properly, we first need a quick overview of contemporary meta-ethics. In Week 3, we discussed realism and anti-realism with respect to the external world. Similarly, we can now distinguish between moral realism and moral anti-realism. According to moral realists, there are objective moral values or normative facts, independent of subjective opinion. Moral anti-realist deny this. Within moral realism, we can make a further distinction between ethical naturalism and ethical non naturalism. According to ethical naturalists, moral properties are not only objective, but they can also be reductively analyzed in terms of non-moral properties. Utilitarians, for instance, hold that good can be reduced to or analyzed in terms of the greatest happiness for the greatest number. Ethical non-naturalists, by contrast, believe that moral properties are not only objective, but also irreducible, an analyzable, or in a formulation that we learned in a previous module primitive. To make matters more complicated. There is a further divisive issue in meta-ethics. Cognitivism versus non-cognitivism. Cognitivist theories assert, and non-cognitivist theories deny that ethical claims express propositions and hence can be true or false. For the most part, the distinction between cognitivism and non-cognitivism parallels that's between realism and anti-realism. All realist theories are cognitivist theories, but not the other way round. An odd one out is the Error theory developed and defended by Mackey. Its core idea is that, although ethical claims express genuine propositions and hence can be true or false, all of them are systematically false. The Error theory combines cognitivism, or ethical claims assign moral properties to the world with anti-realism, since there are no more properties out there or ethical claims are false. Let's complete our big picture overview of meta-ethical views with three views that are in line with the indicated parallelism, both anti-realist and non-cognitivist. The first one chronologically is emotivism, developed and defended by the logical positivists Ayer, insisting on the verificationsm of the logical positivists. He takes ethical sentences not as unverifiable metaphysical assertions, but rather as expressions of approval or disapproval. Murder is wrong, simply means boo to murder, hence also the theories nickname the hurrah boo theory. Subsequently, prescriptivism developed and defended by Ayer, considers ethical sentences to be concealed imperatives, so that murder is wrong, boils down to don't murder. Finally, quasi-realism, developed and defended by Simon Blackburn. It holds that ethical statements project emotional attitudes onto the world as though they were real objective properties. Although conceptual thought experiments flourish in meta-ethics, we will only discuss one, though, a very important one, both historically and methodologically. The publication of G E Moore's Principia Ethica in 1903, heralded the start of the meta-ethical debate that we've just sketched briefly. In his opus magnum, Moore mounts an attack on ethical naturalism, not only in all of its actual forms, but even in all of its possible forms, and argues for his non-naturalism as the only viable alternative. According to Moore, ethical naturalists theories are bound to commit the naturalistic fallacy. Reminiscent of Hume the naturalistic fallacy is often considered to be the failure to recognize the gap between is and ought, or between facts and values. But Moore's open question argument reveals that he has something deeper in mind. Now, let's consider Moore's arguments. Consider the following two by conditionals. First, A is good if and only if A is good, and then A is good if and only if A is bringing about the greatest happiness for the greatest number, the latter being how utilitarians conceive of goods. Now, the first sentence is trivially true. But the second one is true, is according to Moore, an open question that is, a conceptually competent person may very well question whether A is good, and A is bringing about the greatest happiness for the greatest number, are equivalent. From the previous clips, we've learned that conceptually competent people can quite easily think of imaginary counter-examples to propose analysis of goods. Most open question argument is a meta thought experiments, or a generic thought experiments. Whatever non-trivial analysis of good we consider, we can always imagine a conceptually competent person for whom that analysis is and remains an open question, or on the safe assumption that we are ourselves conceptually competent people. Whatever analysis we consider, we will be able to conceive of imaginary counterexamples. We seem left with only two options. Either we accept Moore's primitivism about goods, or we throw in the towel on moral realism altogether.