There is no compelling reason to believe that objective moral facts exist.

Introduction The only definition necessary is of "objective moral fact": a moral truth (e.g. "human life is morally valuable", "theft is wrong", etc. which is independent of the human mind and is categorically binding. An example of an objective non-moral fact is the equation 2 + 2 = 4. Even if there are no minds around to grasp and process this fact, it remains true. The DDO community has heard me debate nihilism again and again, however, and I trust that my meaning is understood (i.e. that no semantic arguments will be employed). Whether there is a "compelling reason" to believe in the existence of moral facts, while up to the voters, must be determined on the basis of arguments presented here, rather than on the ethical leanings of each voter. The position I'll be defending is Moral Nihilism, which expresses the proposition that moral facts do not exist. My opponent, on the other hand, will be defending the opposite proposition--that objective moral facts do exist. He may use any theory he pleases (e.g. utilitarianism, deontology, virtue ethics) to support his argument. The nihilistic argument is three-pronged: we'll look at normative contingency, the presupposition problem, and the subjective value problem. 1. Normative contingency This is pretty straightforward. Normative contingency simply asserts that our moral judgments and normative theories are all contingent on whatever our ethical values happen to be. This is a fact which most everyone acknowledges; however, if we consistently apply this concept, we also see that moral values are themselves contingent, usually on one's psychological states, personal interests, etc, and cannot therefore be regarded as objectively morally binding. I should point out that, though this argument may perhaps look similar to a fallacious appeal to motive, I'm not discrediting moral propositions on the basis of values being psychologically or emotionally motivated: I'm discrediting such propositions on the basis of values being fundamentally arbitrary propositions. There's no objective reason to assume that human life is morally valuable any more than there is a reason to assume that universal death is the ultimate value--such things are simply assertions which must be assumed in order to build a moral theory. Being assumptions, fundamental moral principles--upon which all secondary moral "facts" are contingent--are merely taken for granted (often collectively, as in the case of first principles such as "human life is valuable), rather than logically defended. Given that fundamental moral values are necessary arbitrary assertions, and therefore contingent on some subjective mental process, the nihilist position appears already to have a strong foothold. 2. Presupposition problem This is also a fairly brief argument which merely points out that anyone arguing for moral truth must necessarily presuppose the existence of objective moral facts in order to assert their existence, which leads to placing an unwarranted degree of necessity upon their existence. To even say that "murder is wrong" implies that objectively-binding values exist. This unspoken implication is the presupposition that, rather than discussing the issue of moral truth, we must take the existence of external values for granted so that we may commit ourselves to the sole task of determining the identity of such values. To clear up any confusion, this differs from normative contingency in that the contingency problem addresses the specific identity of values (and the issue of their arbitrary nature), while the presupposition problem obviously addresses the presupposition that such values do exist in the first place, regardless of their particular identities. 3. Subjective value problem Following the presupposition problem, this argument addresses the possibility of objective moral values. The question is what it means for something to be a value. When one talks of the value of a commodity, for example, we note that the value accorded to it is entirely dependent on market forces. What are people willing to pay, and how much are people willing to accept? Does the value of a commodity outweigh the value that an agent accords to his financial resources? This is, of course, up to the subjective calculations of individual agents. Such is also the nature of values, as solely subjective. In other words, the attachment of value is solely the function of the mind: asking whether something is valuable brings up the questions "valuable to whom and for what purpose?" Consequently, we cannot try to make objective the subjective value judgments of individual agents, nor can we call such judgments universal simply because they may be imposed on others by force. At that point, we are simply substituting one's values for another's values--not establishing moral truth. As value is merely a subjective judgment--a product of the mind--we cannot logically call any value an objective, i.e. mind-independent, property of an object. It may be objected that there are universally-recognized values, such as human life, that suggest the existence of moral facts. However, there are two errors here. The first is simply a logical fallacy, affirming the consequent: The fallacy takes the following form: If A, then B. B, therefore A. In this case, the objection would be phrased as: "If X is an objective moral value, it will be universally-recognized. X is universally recognized, therefore it is an objective moral value." There are cases in which affirming the consequent can be a legitimate argument form, but those cases only occur when A is the only possible condition for B. Since objective moral truth is not logically the only possible condition for universal recognition; ergo, citing universal recognition is not sufficient grounds to claim objective moral values. This, of course, assumes the truth of the premise (that objective moral values would be recognized), which is itself quite debatable. The second problem is that collective subjectivity is not the same as objectivity. Briefly stated, it is not necessarily the case that X (say, murder is wrong) is an objective moral fact merely because some number of individuals claim that it is. A mass ipse dixit is no less a bare assertion than a lone individual making the same claim. By the same logic, we would have to accept that the fact of pluralism--which is simply a descriptive statement about the plurality of different moral codes--indicates that there is no objective moral truth. Though some nihilists or relativists may stoop to this kind of argument, I will not, and will simply point out that the converse not only suffers from similar issues, but also hopefully makes the this potential objection easier to understand (and reject). Conclusion On three separate counts, it appears that nihilism makes a powerful case for rejecting the concept of objective moral truth, facts, values, or whatever you would care to refer to such as. Based on my analysis, and on the responses to potential counterarguments, I feel confident that any argument attempting to demonstrate moral objectivity will encounter challenging--if not insurmountable--obstacles.