I have a bold claim:

To measure the depth of a person’s thought is, to a certain degree, to measure the depth of their moral philosophy.

I. Why Do We Need a Metaphysics of Morals?

Moral philosophy covers an enormous range—nearly every question concerning human beings falls under this category.

In my limited view, law consists of settled moral questions, politics of unsettled ones.

And moral questions exist on multiple levels:

1. Ordinary Moral Knowledge

The shallowest level is ordinary moral knowledge—knowing what to do in what situations.

I’ve met many muddled people in this world, muddled precisely because they’re stuck at this shallowest first level.

Because such knowledge is too closely tied to reality, it may not apply when the context changes.

2. Philosophical Moral Knowledge

Abstract one level up, and you get philosophical moral knowledge—various moral maxims and the like.

The saying “I’ve heard all the advice but still can’t live well” refers to this kind of wisdom.

Even at this step, it’s still not enough. Because these maxims are scattered, unsystematic. Different moral teachings may even contradict each other. When conflicting moral ideas can’t be unified, they only create internal friction, naturally failing to guide one’s life. So we need to go higher.

Going further up, we unify various moral maxims into a complete moral philosophy, forming a school’s general principle that encompasses the individual maxims. For example, utilitarianism’s general principle is the greatest happiness for the greatest number; nationalism’s general principle is the supreme interest of nation and state.

Rising to this level may suffice for many people. But for those seeking firmer ground to stand on, this won’t do. Because you may have noticed that these moral principles ultimately rest on conditions in the sensible world—happiness, interests, and such. So there will always be situations where these real-world conditions fail or no longer hold.

For instance, for those who put nation above all—if your nation becomes Nazi Germany murdering Jews, how do you reconcile yourself? For utilitarians, does pursuing the greatest happiness for the greatest number mean you can freely insult and harm the minority?

So even though we’ve abstracted from knowledge to principles, and from principles synthesized into systems, it’s still not enough. We need a higher guiding principle that excludes all empirical reality.

4. Metaphysics of Morals

For something to be called morality, it must apply to everyone, be universally valid. Otherwise your morality only applies to yourself, because not everyone shares your conditions, and you can never fully comprehend others’ joys and sorrows. If that were the case, no one would have the standing or right to criticize or make demands of others—morality would slide into nihilism.

But if you still cannot fully believe that everything is beyond right and wrong, good and bad; if you don’t think people can murder, burn, rape, and cannibalize at will—then you absolutely cannot claim morality is subjective or nihilistic. You still hold an objective moral stance, believe in universal values.

For our morality to be universally valid, applicable to all people; for your stance to rest on absolutely solid foundations, unassailable no matter what, so no one can easily sway you—

You absolutely cannot build moral principles on anything conditional. They must arise from pure reason, unmixed with any real-world factors. They cannot be based on changeable things like practical interests or emotional preferences.

This supreme principle of morality must be an unconditional axiom, founded on humanity’s most essential attribute.

And humanity—indeed all rational beings—has as its most fundamental attribute freedom: the capacity to possess purposes and will independent of natural laws.

Every person, regardless of status high or low, wealth great or small, intelligence wise or foolish, capability large or small, has their own will. Heroes and great figures can have their world-changing ambitions; ordinary people can have their own small, simple wishes. The capable have greater degrees of freedom, the less capable have smaller ranges of choice—but never none at all.

This thing that exists in every rational being and is never absent—this is the foundation for morality’s objective existence rather than nihilism.

This freedom—regardless of its magnitude—the ability to generate self-awareness and purpose independent of natural laws, is the fundamental attribute distinguishing humans from things.

And morality is the law of freedom.

Compare: with natural law, natural objects acted upon by external forces produce results according to natural laws. With moral law, free will through self-legislation produces the results of that will.

And this concept of free will legislating for itself is the supreme principleof Kant’s metaphysics of morals:

Act only according to that maxim through which you can at the same time will that it become a universal law.

Kant’s phrasing is convoluted, but to translate it into Chinese idiom, what immediately comes to mind is that phrase from ancient Chinese scholars—”establishing a heart for heaven and earth.”

What heart does heaven and earth have? None—they’re beings without reason or emotion. It was simply those scholars wanting to make their own principles into universal laws, to impose their Confucian ideals upon all living beings.

But this is perfect for understanding Kant’s metaphysics of morals.

From prime ministers and emperors down to peddlers and laborers, all hope the moral principles they uphold become universal law. Dictators need no explanation—they wish all under heaven would worship their names, that they could command the world with none daring to disobey, unable to tolerate half a word of dissent. Village wives and common folk also have their methods of asserting their will—endless open attacks and hidden schemes against whatever doesn’t suit them. Even the most peaceful liberals have their own inviolable moral bottom lines and hope everyone observes them.

Morality, plainly speaking, is the path a person chooses for themselves when facing various free choices, guided by the principles they’ve set for themselves.

Because of freedom, humans can generate will and purposes independent of natural laws. Free will is the cause, realization of purpose is the effect, and what connects cause to effect is moral law.

II. Why Should We Obey Moral Law?

But moral law gives us no absolute reason we must obey it.

Many things you clearly know are right to do, yet they come with no absolute reason you must do them.

Crime pays, virtue starves. (As the proverb goes: “Murder and arson bring golden belts, building bridges and repairing roads leave no corpse behind.”)

Adhering to morality doesn’t guarantee happiness or joy—often quite the opposite.

So why on earth should I obey this damned moral law that brings no benefit?

Morality comes from the intelligible world (Plato’s Republic / the realm of Ideas / Kingdom of Ends / the world of ought). Interest points toward the sensible world (reality / the world of is).

An absolute reason for obeying moral law is something absolutely incomprehensible to us.

Suppose we discovered this absolute reason one day—then moral law would become natural law.

What we ought to do and what we actually do would be completely identical—that would eliminate freedom.

If everything is predetermined, what freedom is there to speak of?

Even with Buddhist karmic retribution, your very decision to accumulate merit and do good deeds would no longer be your free will. All your actions would be governed by that absolute reason, all your behavior subject to natural laws, unable to make any independent decisions. Originally you had the choice of whether to lay down the butcher’s knife, but in a world where absolute reasons exist, even that decision isn’t yours—it’s predetermined by an invisible hand.

So as long as humans remain free, the necessity of obeying moral law—this absolute reason—lies beyond the limits of reason, belonging to what human reason absolutely cannot comprehend.

So then, since I am free, why should I voluntarily take on morality’s shackles?

Even if my reason can understand what moral law is, if it can’t bring me any visible benefits, why must I unconditionally obey it?

There is no reason, says Kant.

If such a reason existed, it would eliminate freedom—humans would be no different from any other natural object.

But precisely because there’s no practical reason for it, it also has no price tag.

What is raised above all price, and therefore admits of no equivalent, has a dignity.

—Immanuel Kant

References:

Deng Xiaomang: Reading Guide to Kant’s Groundwork of the Metaphysics of Morals, People’s Publishing House, 2012

Immanuel Kant, Mary Gregor: Groundwork of the Metaphysics of Morals, Cambridge, 2012