# Section I: Moral Distinctions Not Derived from Reason explained — A Treatise of Human Nature

> Chapter companion for A Treatise of Human Nature by David Hume.

## What happens

In this section, Hume argues that moral distinctions are not derived from reason but from sentiment. He challenges the view that morality consists in relations discoverable by reason, showing that such relations can apply to inanimate objects, and that reason alone cannot influence action. He introduces the famous is-ought problem, noting that moral systems often move from descriptive statements to prescriptive ones without justification.

## Themes in this chapter

### Morality as Sentiment

Hume argues that moral distinctions arise from sentiment, not reason, and that vice and virtue are perceived by feeling, not by rational demonstration.

### Skepticism About the External World

Hume's skepticism about reason's ability to discover moral relations parallels his broader skepticism about causal connections and external objects.

## Character check-ins

### David Hume

Hume presents his argument that moral distinctions are based on sentiment, not reason, and introduces the is-ought problem.

## Key lines

> I cannot forbear adding to these reasonings an observation, which may, perhaps, be found of some importance. 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 .

Hume observes that in all moral systems, authors transition from descriptive statements (is/is not) to prescriptive ones (ought/ought not) without explaining how this new relation is derived, which he finds problematic.

_This is the famous is-ought problem, a key contribution to moral philosophy._

> So that when you pronounce any action or character to be vicious, you mean nothing, but that from the constitution of your nature you have a feeling or sentiment of blame from the contemplation of it.

Calling something vicious means you feel blame toward it, not that you have discovered a rational property.

_Hume's sentimentalist view of morality._

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