Laws of Nature

Laws of nature, such as the law of gravitation, seem to govern what happens and support counterfactuals. This topic asks what distinguishes a genuine law from an accidental regularity and what laws fundamentally are.

Definition

A law of nature is a true generalization that is not merely accidental but supports counterfactuals and explanation; theories of lawhood explain what gives a regularity this status.

Scope

Covers the Humean best-system analysis, the Dretske-Tooley-Armstrong account of laws as relations among universals, dispositionalist and governing conceptions of laws, and Cartwright's challenge that fundamental laws are not literally true.

Core questions

• What distinguishes a law from an accidental regularity?
• Do laws govern nature or merely describe its patterns?
• Are laws reducible to non-modal facts, or irreducibly modal?
• Are the fundamental laws of physics strictly true?

Key concepts

• Lawhood
• Accidental regularity
• Best-system analysis
• Necessitation relation
• Governing conception
• Ceteris paribus laws

Key theories

Humean best-system analysis

Following Mill, Ramsey, and Lewis, laws are the regularities entailed by the deductive system that best balances simplicity and strength in describing the world; lawhood supervenes on the total distribution of non-modal facts.

Laws as relations among universals

Dretske, Tooley, and Armstrong hold that a law is a higher-order necessitation relation between universals, which underwrites and explains the corresponding regularity rather than merely summarizing it.

Skepticism about fundamental laws

Cartwright argues that the fundamental laws of physics are true only of idealized models and 'lie' about concrete situations, so explanatory power and truth come apart at the fundamental level.

History

The Humean tradition treats laws as especially good regularities, systematized in the Mill-Ramsey-Lewis best-system analysis. In the late twentieth century Dretske, Tooley, and Armstrong proposed that laws are relations among universals. Cartwright and dispositionalists further challenged the standard pictures of lawhood.

Debates

Do laws govern or merely describe?

Humeans hold that laws are summaries supervening on the mosaic of particular facts; anti-Humeans hold that laws involve genuine necessitation or powers that govern and explain the regularities.

Key figures

• David Lewis
• D. M. Armstrong
• Fred Dretske
• Michael Tooley
• Nancy Cartwright

Seminal works

• armstrong1983
• cartwright1983

Frequently asked questions

What is the difference between a law and an accidental regularity?

Both are true generalizations, but a law supports counterfactuals and explanation ('if this were released it would fall'), whereas an accidental regularity ('every coin in my pocket is silver') does not. Theories of lawhood try to say what underlies this difference.