Almost everyone wants other people to follow the same moral code that they do. Life would be a lot easier that way. Unfortunately, which moral code other people are supposed to follow varies dramatically depending on whom you ask. Is this simply a matter of irreconcilable differences in subjective perspective, or are some people objectively right about which morals everyone should follow? Let’s find out.

Objective truth consists entirely of facts (one fact = one piece of objective truth, all facts = all objective truth), so if morality has an objective basis, it has to have a basis in facts. There have to be facts that can tell us what’s morally right and wrong. Do such facts exist?

Any attempt to answer that question with a “yes” must contend with what is called the “is-ought gap” in philosophy. The is-ought gap was first formulated by the eighteenth-century Scottish philosopher David Hume in A Treatise of Human Nature:

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 surprized 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 is 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.

In other words, there’s no way to deduce a conclusion about what one ought to do (a moral value) exclusively from a statement about what something is (in this context, a fact). The mere fact that something is a certain way doesn’t tell you anything about what it should be.

For example, if you’re thinking about chopping down a tree and want to figure out whether that would be right or wrong, there are no facts that can answer that question. It might be a fact that you want to chop down the tree, but that just begs the question: should you or should you not act on that desire? It might be a fact that the tree would provide firewood for your family during a cold winter, but that, too, just begs the question: should you or should you not want to keep your family warm? If you read that last question and exclaimed, “Of course you should want to keep your family warm!” then very well, but note that you’ve answered that question by an emotion, not by a fact.

Now, assuming that you do want to keep your family warm through the winter, the fact of the tree’s suitability for firewood is a relevant one to know, and may influence how exactly you act on your desire to provide for your family. In other words, that fact may influence the means by which you apply your moral impulse to the situation in which you find yourself. But the fact is still just a means to an end; it can’t tell you whether the end itself is a good one or a bad one.

Our moral values arise from our desires. Even when our values constrain our desires, this is at bottom one desire or set of desires constraining another. After all, how else would we care about a value enough to adhere to it in the face of internal opposition? To care about something necessarily means to desire something.

The desires that give rise to our values are not facts; while they may correspond to particular objective phenomena such as neural activity and outward manifestations in body language and action, they themselves are aspects of our subjective experience. How could the values that are extensions of our desires be anything but subjective as well?

There are, of course, facts about desires – Person A desires X, desire Y corresponds to activity in Z part of the brain, etc. – but in and of themselves, such facts about desires have nothing whatsoever to tell us about what we should or should not desire. They face the same insurmountable problem as all other attempts to derive a “should” from an “is.”

Even when we scientifically study the history, sociology, psychology, and neuroscience of morality, all that gives us is a larger pile of “is” statements, and we still can’t derive a “should” from that research alone. If, for example, there are facts of biology or psychology that can explain why you want something that you want, pointing them out is still just a factual argument about what you do want, and does not and cannot pronounce on whether or not you should want it.

Furthermore, even if we could conclusively prove the objective existence of an all-powerful being who has given us a moral law to follow (which we can’t), this, too, would just beg the question: why should we follow this being’s directives? If he condemned us to an eternity of suffering for breaking his moral law, should we or should we not value our moral independence more highly than the manner in which we spend eternity? Regardless of how we answer that question, we answer it with our desires, not facts, whether real or hypothetical.

People want their morality, whatever it is, to be objectively true for persuasive purposes. If morality is subjective, then people have to share your desires in order for your moral arguments to be persuasive. Since desires vary dramatically from one person to the next, there will inevitably be some people who don’t share your desires, and those people will simply never be convinced by your moral arguments. But if morality is objective, then you can demonstrate to other people that your morals should be followed in the same way that you can demonstrate that water will boil when heated to a certain temperature. As we’ve now amply seen, however, there’s no way to do that.

Paradoxically, then, the argument for an objective morality ultimately isn’t an empirical argument, but a normative one. It’s based on desires rather than facts. And that in and of itself underscores my – and Hume’s – point.

Admitting that morality is subjective doesn’t necessarily imply that it’s a matter of choice. There are certain things that I sense to be right or wrong so viscerally that, for me, those moral values are as immutably true as the fact that I have two hands. I don’t “choose” them to be right or wrong any more than I choose to have two hands. But while there’s a way that I could demonstrate to others beyond any plausible doubt that I believe in those values, there’s no way that I could prove to anyone else that those values themselves are the right ones to hold.

I’d rather see that truth clearly for what it is and state it plainly than obscure it out of fear of what some other people might do with it. That’s a reflection of my own subjective values. Others may make the opposite call, and if so, then so be it. But they can’t then claim to value the truth above social expediency.

Just because something is subjective doesn’t make it flippant or worthless, as we all too often tend to think. Quite the contrary: when it really comes down to it, the subjective matters much more than the objective, as I argue in my book The Language of Meaning: Why Science Cannot Replace Religion. Knowing a fact is just a means to an end; knowing and experiencing what’s preeminently meaningful, by contrast, is the end of all ends.