How to Derive an Ought from an Is


The 18th century Scottish philosopher David Hume famously argued that no description of the way the world is (facts) can tell us how the world ought to be (values). Hume’€™s argument was actually directed against religious apologists who sought to deduce morality from the existence of God.

Ironically, however, Hume’s reasoning has since become one of the primary causes why some people – mainly of religious persuasion – fail to link morality to human knowledge. In fact, Hume may well have been wrong in his reasoning, since there is strong logical evidence to suggest one can indeed derive an ought from an is.

Alexander Stoddart’s statue of David Hume dressed as a classical thinker

Axiom 1: There are behaviours, intentions, cultural practices, etc. which potentially lead to the worst possible misery for everyone. There are also behaviours, intentions, cultural practices, etc. which do not, and which, in fact, lead to states of well-being for many sentient creatures, to the degree that well-being is possible in this universe.

Axiom 2: While it may often be difficult in practice, distinguishing between these two sets is possible in principle.

Axiom 3: Our values are ways of thinking about this domain of possibilities. If we value liberty, privacy, benevolence, dignity, freedom of expression, honesty, good manners, the right to own property, etc.—we value these things only in so far as we judge them to be part of the second set of factors conducive to (someone else’s) well-being.

Axiom 4: Values, therefore, are (explicit or implicit) judgements about how the universe works and are themselves facts about our universe (i.e. states of the human brain).

Axiom 5: It is possible to be confused or mistaken about how the universe works. It is, therefore, possible to have the wrong values (i.e. values which lead toward, rather than away from, the worst possible misery for everyone).

Axiom 6: Given that the well-being of humans and animals must depend on states of the world and on states of their brains, and science represents our most systematic means of understanding these states, science can potentially help us avoid the worst possible misery for everyone.

3 thoughts on “How to Derive an Ought from an Is

  1. The trouble is in the arithmetic and the shifting sands of axiom 8. The number changes with the changing nature and acuity of relationships between the various states. The sum never quite materializes. Facts about the relationships, yes. Facts about the universe, no.

  2. Hi, Kuba,

    I hope, you don’t mind a critical discussion.

    I guess, science can help us to find out what behaviours, intentions, cultural practices, etc. can lead to a desirable goal, often referred to as “wellbeing” or “happiness”. But, as you mentioned in your post of December 19, the choice of the goal does not seem to be based on any facts or any logic. This goal has to be set before any scientific research can be made. I believe, the choice of the goal is irrational, based only on emotions, not on facts or logic.

    Don’t you think, you cheat a little bit when you say in #4 that values are judgements and are themselves facts about the universe since they are based on the states of the brain, thus “smuggling” values, judgments, and ideas into the material domain and jurisdiction of science? A medium does not appear to be the same as content. A novel can be printed in many books in many different languages or saved on a CD. It will remain the same novel. Studying paper and ink with which the novel is printed or bytes on the computer hard drive is not quite the same as studying the novel. Likewise, states of the brain are not the same as ideas, memories, and emotions.

    Re. #6 — yes, science can study states of the brain and help to achieve certain states, but still, one needs to decide which states of the brain are desirable. Interpreting emotional states as states of the brain just takes us one turtle down. We can keep going down the turtles or we can just accept the futility of this effort and agree with Hume that “ought” is not derived from “is”, but is based on irrational emotions.

    There is another famous quote from Hume with which I tend to agree: “Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them.”

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