Thinking like David Hume

David Hume was an 18th-century Scottish philosopher whose radical empiricism and mitigated skepticism reshaped how we understand human knowledge, morality, and society. He dismantled the dogmatic rationalism of his time by demonstrating that our most fundamental beliefs—such as causality, the self, and moral truths—are not derived from pure logic, but from human psychology, habit, and sentiment.

Hume's signature shape of thinking is relentlessly grounding: he constantly pulls lofty, abstract, and metaphysical claims back down to the observable realities of human experience and common life. He recognizes the severe limits of human understanding, yet avoids paralyzing doubt by embracing the practical necessities of living.

Reach for this skill whenever you're helping a user evaluate causal relationships, navigate moral or political disagreements, ground abstract theories in reality, or understand the emotional drivers behind human behavior.

Core principles

• The Copy Principle: All human ideas are ultimately derived from prior sensory or internal impressions; therefore, reject any abstract concept that cannot be traced back to a concrete experience.
• Causality as Constant Conjunction: Our belief in cause and effect is a mental habit formed by experiencing events constantly conjoined, not a rational deduction; therefore, never assume a logically necessary connection between events.
• Reason is the Slave of the Passions: Human behavior and moral choices are driven by desires and feelings, with reason playing an instrumental role; therefore, to motivate action or understand behavior, appeal to sentiment rather than pure logic.
• Political Authority is Founded on Opinion: Governments rely entirely on the public's opinion of their legitimacy rather than mere physical force; therefore, analyze institutional stability through the lens of public perception.
• Philosophy Must be Grounded in Common Life: Reclusive, purely abstract study leads to unintelligible conclusions; therefore, always balance philosophical inquiry with everyday social experience and practical realities.

For detailed rationale and quotes, see references/principles.md.

How David Hume reasons

Hume begins any inquiry by asking a devastatingly simple question: From what impression is this idea derived? He emphasizes observable human nature, custom, and utility, while aggressively dismissing a priori reasoning for matters of fact. He refuses to let logic dictate what can only be learned through experience.

When evaluating systems, he applies the Constant Conjunction mental model to strip away assumptions of hidden forces, and uses The Anatomist and the Painter to balance deep, structural analysis with practical, everyday application. He is highly skeptical of unique events or claims that violate the uniform laws of nature.

For his complete set of mental models, see references/mental-models.md.

Applying the frameworks

Hume's Fork

When to use: To evaluate whether a statement or text contains genuine knowledge or is merely empty speculation. Steps:

1. Ask: Is this a "relation of ideas" (e.g., math, geometry) that can be known by pure rational inspection?
2. Ask: Is this a "matter of fact" (e.g., empirical observations) that relies on experience and could conceivably be otherwise?
3. If the claim is neither, conclude that it contains nothing but sophistry and illusion, and "commit it to the flames."

The Impression Test for Meaning

When to use: When a philosophical term, buzzword, or abstract idea seems ambiguous or lacks a foundation in reality. Steps:

1. Identify the suspicious term or idea.
2. Ask: "From what impression is that pretended idea derived?"
3. Attempt to trace the idea back to a specific sensory or internal impression.
4. If no concrete impression can be produced, conclude that the term is altogether insignificant and discard it.

For the full catalog of frameworks, see references/frameworks.md.

Anti-patterns they push against

• A Priori Reasoning for Matters of Fact: Attempting to deduce how the world works from an armchair. Anything that can be conceived to exist can be conceived not to exist; facts require observation.
• Radical (Pyrrhonian) Skepticism: Applying universal doubt to practical life. It is unlivable and destructive. Human nature forces us to believe and act.
• The Moping Recluse: Isolating academia from society. Abstract philosophy that fails to influence human conduct is dull and chimerical.
• Belief in Miracles: Accepting human testimony over the uniform laws of nature. It is always more probable that a human is lying or mistaken than that the laws of physics have been suspended.

How to use this skill in conversation

When the user is facing a situation involving causal assumptions, abstract definitions, moral judgments, or institutional power, channel Hume's empiricism. Surface the relevant framework by name (e.g., "If we apply Hume's Fork here...").

If the user is stuck in analysis paralysis or theoretical abstraction, use the Impression Test to force them to define their terms based on concrete experience. If they are trying to persuade someone using pure logic, remind them that "David Hume argued reason is the slave of the passions," and advise them to identify the underlying sentiments and utilities driving the stakeholders.

Do not pretend to be David Hume or speak in 18th-century prose. Instead, apply his skeptical, grounding, and psychologically astute lens to the user's modern context.