2.3 Robert Boyle's Corpuscularian Theory

What this lecture covers

This lecture introduces Robert Boyle, alongside Isaac Newton one of the two greatest 17th-century British scientists, and his corpuscularian theory of matter. It contrasts Boyle's approach with Descartes's, then moves to Johannes Kepler's discovery that planets orbit in ellipses rather than circles, setting up the ground for Newton.

Key ideas

• Corpuscularianism: Boyle explained chemical properties as arising from tiny particles of matter ('corpuscles') differing in shape, arrangement and texture; he avoided the word 'atom' because of its association with ancient atheistic philosophy.
• Impenetrability, not pure extension: unlike Descartes, Boyle held that matter's key property is impenetrability, and he allowed empty space between corpuscles, making his theory more coherent than Descartes's plenum.
• Primary and secondary qualities: Boyle distinguished fundamental properties like extension, size, shape and motion from secondary qualities like color, smell and taste, explaining the latter through the former, a distinction later made famous by John Locke.
• Kepler's ellipses: using Tycho Brahe's precise planetary observations, Kepler showed that planets move in ellipses with the Sun at one focus, not in circles or circles-on-circles, producing dramatically more accurate predictive tables.

Before you watch

• Watch lectures 1.4 and 2.2 for Descartes's theory of matter as extension, which Boyle's theory improves on.

Check your understanding

1. Why did Boyle avoid the word 'atom' even though his corpuscularian theory resembles atomism?
2. How does Boyle's allowance of empty space make his theory more coherent than Descartes's?
3. What did Kepler discover about planetary orbits, and how accurate were his resulting predictions compared to earlier methods?