David Hume and the Is/Ought problem

4 min readFeb 2, 2021

David Hume was a 18th century empiricist Scottish philosopher. One of his early works was A Treatise of Human Nature, published in 1739. This was not received well by critics. In his memoirs, My own life, published in 1776, just a few months before his death, he mentions:

Never literary attempt was more unfortunate than my Treatise of Human Nature. It fell dead-born from the press, without reaching such distinction, as even to excite a murmur among the zealots. But being naturally of a cheerful and sanguine temper, I very soon recovered the blow, and prosecuted with great ardour my studies in the country.

He always sounds like such a happy guy! Even while he was dying of stomach cancer, he states:

To conclude historically with my own character. I am, or rather was (for that is the style I must now use in speaking of myself, which emboldens me the more to speak my sentiments); I was, I say, a man of mild dispositions, of command of temper, of an open, social, and cheerful humour, capable of attachment, but little susceptible of enmity, and of great moderation in all my passions.


I consider, besides, that a man of sixty-five, by dying, cuts off only a few years of infirmities; and though I see many symptoms of my literary reputation’s breaking out at last with additional lustre, I knew that I could have but few years to enjoy it. It is difficult to be more detached from life than I am at present.

When he later published An Enquiry Concerning Human Understanding in 1748, he met with far more success. Some critics still referenced his earlier work, however, which really pissed him off, causing him to add the following to the start of the book:

Yet several writers, who have honoured the Author’s Philosophy with answers, have taken care to direct all their batteries against that juvenile work, which the Author never acknowledged, and have affected to triumph in any advantages, which, they imagined, they had obtained over it: A practice very contrary to all rules of candour and fair-dealing, and a strong instance of those polemical artifices, which a bigoted zeal thinks itself authorized to employ.

Such complaints addressed at critics seem to have been a fairly common aspect of philosophers. Kant, in his Prolegomena to Any Future Metaphysics That Will Be Able to Present Itself as a Science (let’s just refer to it as the Prolegomena from now on!) complains about thinking his ideas are too obscure, remarking:

In conclusion, let it be remembered that this much-abused obscurity (frequently serving as a mere pretext under which people hide their own indolence or dullness) has its uses, since all who in other sciences observe a judicious silence, speak authoritatively in metaphysics and make bold decisions, because their ignorance is not here contrasted with the knowledge of others.

I personally find these snippets of personality in historical sources fascinating. Whether it’s graffiti at Pompeii, poems by Catullus or Martial, or Socratic dialogues, it’s amazing to see how similar people are, throughout history. Hume himself comments on this:

Would you know the sentiments, inclinations, and course of life of the Greeks and Romans? Study well the temper and actions of the French and English: You cannot be much mistaken in transferring to the former most of the observations which you have made with regard to the latter. Mankind are so much the same, in all times and places, that history informs us of nothing new or strange in this particular.

Returning to the original topic — we can again directly quote Hume’s Treatise on this:

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 line of argument is called this Is/Ought problem. Let’s have an example of this.

  1. The house is on fire.
  2. Therefore, you ought to go out.

Premise (1) seems to imply (2), but this is not correct, according to Hume. Why should one go outside if the house is on fire? Well, clearly, because they don’t want to get burned. That concept is so natural, that it is considered as implicit. The real argument is:

  1. The house is on fire.
  2. If the house is on fire, you ought to go out.
  3. Therefore, you ought to go out.

(1) is a regular premise, or a fact, while (2) is a moral premise — it prescribes some action. Let’s consider one which is less obvious and implicitly assumed:

  1. Someone is in need of aid.
  2. If someone is in need of aid, you ought to help.
  3. Therefore, you ought to help.

Now, here, (1) is a fact — we can come up with a lot of scenarios where it’s pretty undeniable. However, (2) is debatable. For example: should you sacrifice yourself to help someone else? Or if someone is in need of help on an exam, ought you help him by cheating?

Hence, the second premise stating the connection between is and ought is determined by a moral system: a system mapping facts to desired behaviors.

Particularly because the moral premise is usually taken as implicit, it’s interesting to pay attention to it. Oftentimes, in discussions, it’s tough to argue with (1), while (2) is never even mentioned, so that (3) is accepted without consideration.

If you get into the habit of looking into this closer, you tend to discover some pretty abhorrent reasoning in people (and yourself!).