People who believe in the is-ought problem consider deriving normative claims from descriptive claims an informal fallacy. They call it the Is-Ought fallacy and sometimes the Naturalistic fallacy. It is sometimes confused with the appeal to nature fallacy.
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 ways of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when all 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, 'tis 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
In here, David Hume saw an apparent gap between an argument that consists of solely descriptive statements with a normative conclusion. That is, he saw such arguments as a Non-sequitur.
Responses and criticisms:Edit
One response to the is-ought problem is that we can derive an ought from an is if we are analyzing goals. They suggest the following argument form: In order for agent A to achieve goal B, A reasonably ought to do C. A counterargument that some use against this response is that it destroys the difference between goals and morality.
- ↑ Hume, David (1739), A Treatise of Human Nature, p.335