I was discussing the is-ought problem with a friend and to sharpen my thinking I have written this. The writing style is a homage to Hume.

Philo: The so called “is-ought problem” divides propositions into prescriptive and descriptive statements. Prescriptive statements describe justified moral actions and are commonly stated as “what you should do”. Descriptive statements might succinctly be defined as non-prescriptive propositions and they include statements that describe observable reality, as well as non-moral metaphysical propositions. Writers on moral subjects often begin with first principles and descriptive statements that, after much discussion, conclude with the justification of prescriptive statements. In a close analysis of these moral treatise, we may inquire as to which was the first prescriptive statement in their argument and its respective justification. It seems “altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it.” All attempts to bridge this gap by reason have so far failed, and as long as the is-ought problem holds, all moral statements cannot have a final logical basis. This puts laws that guide human actions within the sphere of knowledge but beyond the grasp of philosophers who persist in their attempts to find justification from first principles.

Cleanthes: How absurd to object to the justification of objective morality, as proceeds from the divine being! The justification is plain from what we understand by the only tenable moral system: moral realism. We agree that moral statements are propositions and it is clear that these statements can either be true or false. The truth or falsity exists independent of our opinions as they have existed for all time and are immutable and perfect due to their divine origin. How can you claim this does not satisfy your requirement for logical justification?

Philo: I will attempt to educe [to work out from given facts] this point and show the infirmity of such a justification. When asked, all men are able to provide justifications for their just actions. These justifications may be codified into general principles that illustrate what a man should do in any particular circumstance. And as admitted by all men of good sense, this standard of righteousness proceeds from the divine mind. Take a particular moral action, say “feeding the hungry” and you claim this action is justified by objective morality. But what are the grounds that may I use as the basis for this justification? Or in direct language, why should men follow the principles of objective morality?

Cleanthes: Isn’t this basis self evident and obvious? We agree that objective morality is universal, divine, timeless and perfect and are therefore the principles that a good man should use as a basis for actions. It proceeds from the definition and divine nature of objective morality that it describes what action should be taken by a man. To use your example of “feed the hungry”, God has created a system of laws which is objective and independent of opinion. One law, or part, of objective morality is the imperative to “feed the hungry”. This action is therefore universally justified, except when other divine laws are at stake and we may be satisfied by this justification. Your semantic objections to what is widely affirmed to be true would seem to me as utterly futile.

Demea: We are agreed on the infinite, good and perfect nature of God, Cleanthes, but I am wondering how man might have certain knowledge of the justification of objective moral law. Since this matter is considered by many to be obvious, while I believe it is not so, I will attempt to illustrate my view on the matter. Consider the most abstract conception of God and we may see that there are few or no properties that proceed automatically from the definition of such an entity a-priori. Since the divine nature is so far removed from our every day experiences, we may gain knowledge of God’s commandments, that is “descriptive objective law”, though what ever means are available to man but we cannot a-priori say that God’s privilege to dictate men’s actions. Although you may argue your case from your limited experience of the world, it is presumptuous to assert that this provides justification to any “prescriptive objective law”, since that would incorrectly apply concepts of human origin on the adorable mysteriousness of the divine nature. We can still ask what is the justification of man following God’s commandments, and it remains upon you, Cleanthes, to support your assertion that we can know that divine law is prescriptively justified.

Philo: It seems to me, that there is a distinction in our usage of the concept objective morality, Cleanthes. You have claimed men should follow divine law because it proceeds from God. I will attempt to clarify our definitions in the hopes of clarifying our thought. Your usage of the concept of objective morality implies the definition of “a system of right and wrong conduct which should be followed” which simply means “actions men should do”. Under this definition, objective morality is a prescriptive statement. When I asked you earlier what was the justification, you stated it is by definition justified by objective morality and by your definition, it clearly is. But can you see that if I ask “why should we feed the hungry” and you answer simply “it is objective morality”, which merely means “it is what men should do”, should you be surprised when this answer fails to satisfy? Your claim that the prescriptive justification of objective morality proceeds from the very definition of objective morality is simply an admission of your argument’s tautology!

Cleanthes: You both seem to argue the most abstract and absurd objections, when all reason, common sense and evidence points to God as being the creator and therefore sovereign in the world. This fact being well known and acknowledged even by yourselves. And you, Demea, claim on one hand that God is king of the world and on the other that we cannot know* God is the king of the world! As for you, Philo, who would not accept the plain and succinct answer to your question, I say: objective law should be followed as it is commanded by the creator and sovereign of the world. This answer is equivalent to my first justification, which you seem to fail to grasp, that is the origin and nature of objective law justifies our following it.

Philo: Which provides the justification for objective law? Its origin or its nature? I have already argued that the nature of objective law cannot, without tautology, be shown to be its own justification. And as for objective morality’s origin, the king of the world, you have shifted your justification to a new concept: the sovereignty of God. But your remark that this argument is equivalent to that which you stated at first, opens this point to the same objections. Why should we follow the commands of a sovereign? That God created the world and he is its lord is agreed, but from this descriptive statement of God, it does not logically follow that men should obey him. In reality, Cleanthes, you keep on the same treadmill of stating X is the justification of Y, where all we can of X is that it is defined as “the justification of Y” and we never reach satisfactory descriptive axioms. We can always ask for the logical justification of X and you are likely to posit W as the justification, and so on. You have so far justified “men should feed the hungry” by claiming “men should follow objective moral law” which is justified by “men should obey God’s sovereignty”. We again ask what is the justification of the latter? Without resorting to infinite regress, we may admit, as is acknowledged among the more discerning philosophers, the derivation of prescriptive statements has not yet been achieved from purely descriptive statements.

Pamphilus: “I cannot but think, that PHILO’s principles are more probable than DEMEA’s; but that those of CLEANTHES approach still nearer to the truth.”

by Anti Citizen PhilONE :)

PS “Murder is wrong” (or “Murder is illegal”) is also tautology. Hint: look up the definition of murder.
*Deliberate straw man here.