Corpuscularianism

Corpuscularianism (from the Latin "corpusculum" meaning "little body") is a set of theories that explain natural transformations as a result of the interaction of particles ("minima naturalia, partes exiles, partes parvae, particulae", and "semina"). It differs from atomism in that corpuscles are usually endowed with a property of their own and are further divisible, while atoms are neither. Although often associated with the emergence of early modern mechanical philosophy, and especially with the names of Thomas Hobbes, René Descartes, Pierre Gassendi, Robert Boyle, Isaac Newton, and John Locke, corpuscularian theories can be found throughout the history of Western philosophy. 
Overview.
Corpuscularianism is similar to the theory of atomism, except that where atoms were supposed to be indivisible, corpuscles could in principle be divided. In this manner, for example, it was theorized that mercury could penetrate into metals and modify their inner structure, a step on the way towards the production of gold by transmutation. Corpuscularianism was associated by its leading proponents with the idea that some of the apparent properties of objects are artifacts of the perceiving mind, that is, "secondary" qualities as distinguished from "primary" qualities. Corpuscularianism remained a dominant theory for centuries and was blended with alchemy by early scientists such as Robert Boyle and Isaac Newton in the 17th century.
In his work "The Sceptical Chymist" (1661), Boyle abandoned the Aristotelian ideas of the classical elements—earth, water, air, and fire—in favor of corpuscularianism. In his later work, "The Origin of Forms and Qualities" (1666), Boyle used corpuscularianism to explain all of the major Aristotelian concepts, marking a departure from traditional Aristotelianism.
The philosopher Thomas Hobbes used corpuscularianism to justify his political theories in "Leviathan". It was used by Newton in his development of the corpuscular theory of light, while Boyle used it to develop his mechanical corpuscular philosophy, which laid the foundations for the Chemical Revolution.
Alchemical corpuscularianism.
William R. Newman traces the origins from the fourth book of Aristotle, "Meteorology". The "dry" and "moist" exhalations of Aristotle became the alchemical 'sulfur' and 'mercury' of the eighth-century Islamic alchemist, Jābir ibn Hayyān (721–815). Pseudo-Geber's "Summa perfectionis" contains an alchemical theory in which unified sulfur and mercury corpuscles, differing in purity, size, and relative proportions, form the basis of a much more complicated process.
Importance to the development of modern scientific theory.
Several of the principles which corpuscularianism proposed became tenets of modern chemistry.