The Is-Ought Gap in Ethics

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. This change is imperceptible; but is, however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, it’s necessary that it should be observed and explained; and at the same time that a reason should be given, for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it. 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.

— David Hume, A Treatise of Human Nature, Book III, Part I, Section I

The is-ought gap, or fact-value gap is a problem that arises in ethics. It concerns the apparent impossibility of deriving normative claims (about how the world ought to be), from descriptive claims (about how the world is). If the is-ought gap cannot be bridged, then that spells disaster for any theory of ethics based purely on scientific inquiry (only is statements), because the is-ought gap tells us that either such a theory says nothing about morals, that is, about how we ought to behave in life; or the gap tells us that such a theory is not purely scientific, and we have included a prior ought claim in our assumptions. This is not to say that science has nothing to say about ethics. Once we have agreed on a set of normative premises, we can use science to find out how to best act in accordance with those premises.

To give an example, let’s say I hold to a consequentialist ethics, that is, I judge the worth of an action by its consequences. To decide on how I should act in any given situation, I must first define the value system I act under. This value is encompassed in that tricky word “worth”. If I say that an action is worthy if it leads to pleasure, or if it leads away from pain, then I have made two ought claims: That people ought to pursue pleasure; and that people ought to shun pain. I can clearly argue for this position based on some notion of human intuition, but I cannot argue for it from just empirical evidence. If I try to argue for it by appeal to some consequence of pleasure as in “Pleasure is good because it leads to X”, or try to argue by appeal to some underlying principle as in “Pleasure is good because it is derived from X”, then I beg the question “Why is X good?”. I can continue the chain in either direction, but I will never reach a closed question without arriving at the tautological “X is good because it is X” (Moore, 1903).

Does the Gap Matter?

If we accept the gap, then we should reject any claim at a purely objective morality. This does not mean, as is sometimes assumed, that morality then becomes purely relative. We can agree to some ethics more than others based on some intuition. That we cannot argue a priori for our intuition at least feels irrelevant. If we do not want to argue through intuition, we can take as our principles a small number of ought statements, derive from them a form of moral calculus, and argue for that moral calculus on the basis of how much people agree with the goodness of the consequences of such a calculus. The point is that even in the absence of an objective morality, it is easier to convince people that the principle “Pleasure is good, and pain is bad” is better than the principle “Things that are yellow are good, and things that are blue are bad”, or at least convince them that color is not a property of morality that we should care about.

In this respect, the is-ought gap does not matter. That normative claims cannot be derived purely from descriptive claims just means that we have to premise at least one normative claim in whatever ethics we develop.

However, the notion that morality cannot be objective sits poorly with some people who would like questions such as “How much money should I donate to charity each year?” to be rationally decidable without prior appeal to a value system. That these people exist is no problem in itself; likely the majority of people believe that morality is objective, but that we have yet to find its object. A problem arises when certain of these people opine on ethics and claim to have discovered a scientific morality without engaging in good faith with the literature. It is because such systems agree with the common belief that morality has to be objective, and because they often offer simple guidelines that many people now believe there is an undeniable truth about an ethics that centers around the self-interest of the individual (Rand, 1961), or the claim that all that humans can reasonably value is their well-being (Harris, 2010).

So at least knowledge of the is-ought gap helps with spotting the demagogues, even if it bears little on the validity of an ethics.

Can we Bridge the Gap?

While I think the is-ought gap cannot be bridged, there are arguments for why it can, and we would expect this given that ethics has been around for at least as long as the written word, while Hume wrote of the gap in the 18th century.

I have talked about the problem of how to decide whether a person is good or bad. This seems hard. What if we restrict our scope? Can we decide if a knife is good or bad? Well, yes. We usually call a knife good if it is able to quickly cut through whatever it is we want to cut, and bad if we have to add elbow grease to the process. A knife is terrible if it doesn’t do its job at all. A spoon is a terrible knife. In other words, a knife is good if it effectively fulfills its purpose to cut objects. To do this, a knife must at the very least be sharp, sturdy, and well-balanced. I can apply a similar argument to living things. The purpose of a tick is to latch onto a host for blood. To do this effectively, it must be able to locate a blade of grass near a well trafficked area, climb onto the blade, drop at the right moment to fall on the host, and find a spot to latch on from which it won’t be removed. The better it does these things, the better it fulfills its purpose.

If we say a thing that fulfills its purpose is good, we can arrive at an ethics if we can answer what the purpose of a human being is. We have no problem answering variants of this question, such as: What is the purpose of the human being as a swimmer, or as a chef, or as a scientist. The question of the purpose of the human being as human being is trickier. You may say that this is just pushing the buck further down to justifying that some purpose is actually the purpose, and I agree, but this has no bearing on the is-ought gap.

The assumption in a teleological account is that the purpose (telos) can be discovered in nature through empirical evidence. If we can arrive at a purpose, and thus at an ethics, merely by looking at how the world is then the gap has been bridged. There is good reason for believing that we can find such a purpose. After all, it isn’t a strange claim to say that the purpose of any individual animal or plant is to act towards the preservation of the species in the face of environmental pressure. Of course this doesn’t satisfy, and such an argument can be perverted to justify monstrous behavior, but the point is that this purpose was arrived at by working from empirical data and looking at animal behavior. This effectively bridges the gap by turning ethics into ethology, and there are ethicists who can be interpreted in this way (Spinoza; Deleuze 1970).

Conclusion

Where does this leave us? If it leads anywhere, it would lead to a profound skepticism. I think this skepticism is more valuable than we give it credit for. Humanity has too often made morality subservient to its needs and used it to justify oppression, and perhaps it is our duty to constantly question whether our actions benefit those they impact. And if our answer to that question is that they do not, then maybe it is time to reevaluate the oughts we have constructed our morality from.

Further Reading

These first three are historical texts that cover the three main forms of ethics: Aristotle’s account focuses on cultivating virtue (virtue ethics); Kant’s ethics revolve around duty (deontological ethics), and Mill is the classic text for consequentialist ethics.

Aristotle, Nicomachean Ethics
Kant, I., Groundwork for the Metaphysics of Morals
Mill, J. S., Utilitarianism

The is-ought gap is a question in meta-ethics, that is, the study of how we study ethics. This book gives a good overview of problems in contemporary metaethics:

Miller, A. (1965), An Introduction to Contemporary Metaethics

References

Spinoza, B., Ethics
Hume, D., A Treatise of Human Nature
Moore, G. E. (1903), Principia Ethica
Rand, A. (1961), The Objectivist Ethics
Deleuze, G. (1970), Spinoza: Practical Philosophy
Harris, S. (2010), The Moral Landscape