“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.”

What does it mean?

Reason calculates relations and facts, and it does not by itself pick a goal, so goals come from the passions and reason's office is to serve them. Serving includes showing that a passion rests on a false belief about what exists or how to get it. A rival reading hears a advice to obey every impulse, but a calm passion can govern a violent one, and reason still cannot mint a motive out of nothing. The sentence is his own English in the Treatise, a deliberate provocation in the argument that reason alone does not move us.

Did David Hume really say this?

The library’s label is Well attested. Hume's own English in A Treatise of Human Nature, book two, part 3, section 3. Reason alone cannot motivate, and it cannot oppose a passion except by serving an end the passions already set. The provocation is deliberate and the wording is secure.

Where it comes from

A Treatise of Human Nature II.3.3

Approximate date: 1739.

How to use it

When someone on a commuter train into London says a purchase was just the rational choice, separate the prices that were calculated from the want the prices were serving. Hume thinks the want was in charge even if the arithmetic was clean. The sentence does not forbid the purchase; It forbids the pretence that reason selected the end as well as the means.

A mindset reading

Slave is a shocking word on purpose, and it is not a recommendation to follow whatever feeling is loudest this hour. He allows calm passions, including a general appetite for good, to restrain violent ones. What he denies is that reason can oppose a passion except by serving some passion, usually by correcting a belief about the world.

Understand the philosophy

This is the hinge of his moral psychology, and it prepares the later claim that moral distinctions are not derived from reason alone. The key term is passion, any feeling that can set an end, including the calm ones that do not feel like storms. Kant will build an opposing picture in which pure practical reason can be motivating by itself. The English of the Treatise is Hume's, and the provocation is intact.

Related

• “Custom, then, is the great guide of human life.”

  Well attested

• “A wise person proportions their belief to the evidence.”

  Paraphrase or translation

• “I never can catch myself at any time without a perception, and never can observe any thing but the perception.”

  Well attested

Related bias. Confirmation bias. Confirmation bias is the tendency to search for, remember, and accept what supports a view you already like, and to skim past what would hurt it. It is not a claim that every belief is stubborn. It is a pattern in how attention is spent.

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