Robert Boyle was incredibly influential in the way he addressed the issues plaguing natural philosophy in the 17th century through his corpuscular hypothesis, primarily laid out in his work The Sceptical Chymist (1661), having the central claim that matter is made up of small particles called “corpuscles”. Boyle’s hypothesis was itself an expression of monism, the idea that a complex reality could be created through a single substance. Though the term “monism” would not be coined until a century later by Christian von Wolff, monist ideas had been explored by ancient Eastern and Western philosophers. During Boyle’s time, the 17th century, there was a large divide in natural philosophy between mystical alchemical practice and the ancient Aristotelian theory. Aristotelian theory, which at this point had held up for nearly 2 millenia, stated that all matter was composed of the four basic elements: earth, water, fire, and air. Alchemists were a group that claimed all natural bodies arise from three principles (called the Tria Prima): sulfur, mercury, and salt. Boyle took issue with both of these theories, finding himself dissatisfied with their lack of scientific grounding in their claims, and also found that there were incredible inconsistencies in the reports of scholars of these philosophies. Therefore, he sought out to experimentally devise a new foundation for basic elements and chemistry as a whole, based on observations, experiments, and reason.
Boyle sets out to establish his corpuscular hypothesis by first tearing down the aforementioned alchemical and Aristotelian theories. He undertook his inquiry by experimentally proving the inadequacies in these older theories. Boyle’s critique of the Tria Prima revolved around the inconsistency that these principles presented themselves. He looked at when chemists decomposed substances, finding that sometimes, sulfur, mercury, or salt did not seem to show themselves. He writes, “…there are divers others so fix’d or compos’d, at least of so strictly united parts, that I have not yet observ’d the Fire to separate from them any one of the Chymists Principles” (Boyle 1661). If these three principles do not show up consistently when all substances are decomposed, then it is implausible to conclude that they are the elemental building blocks of matter. Rather, Boyle concluded that these were more akin to “secondary products”, which are new substances created during processes such as burning. He uses an analogy of burning wood, explaining that “burning destroys wood while generating flame, soot, and ashes”, noting that this does not mean that the ashes were always present in the wood to begin with (Boyle 1661). In critiquing the Aristotelian theory, Boyle found the inconsistency in how the elements were defined to be core issue: what was meant by “earth” for example? To him, these definitions were not useful because they shifted according to the philosopher. He rationalized these elements to be qualities of things, such as their heat and moisture. Boyle argued that these were merely properties of things and not the fundamental building blocks that matter was composed of. This critique also had experimental backing, given that breaking down some substances did not yield these supposedly fundamental four elements. Through dismantling these two theories, Boyle claimed that neither of these could serve as the basis for describing the building blocks of matter.
Boyle was then able to posit his framework for the composition of matter in the form of his corpuscular hypothesis. At its core, Boyle claimed that all matter was composed of small particles that have varying size and motion that he called corpuscles. Corpuscles were actual, physical entities, and not just an abstract notion. The diversity in substances that were observed in nature could then thereby be explained by the differences in the structures that many corpuscles form when put together. Boyle likens corpuscles to the letters of the alphabet to illustrate this concept, given that an incredible variety of words can be created from such a small sample of letters. Boyle expands upon the working of corpuscles further in his 1666 work The Origine of Formes and Qualities, where he attempts to establish how the mechanical action of corpuscles lead to all observable qualities of substances. Boyle vouches for the monist claim that all things in the world are made of matter, and claims that motion is the power that acts mechanically upon matter and brings about its division into distinct parts, which are the corpuscles. Boyle describes motion as the “active principle”, stating that “motion seems to be the chief second cause… and the grand agent of everything that happens in nature” (Boyle 1666). The active principle can be generalized to mean that all change in the universe is a direct result of motion. Corpuscles, while incredibly minute, still retain some qualities, those being size and shape. They also transfer motion during collision, since “such particles, because they are so small and solid, are hardly ever broken up… we can in this sense call them ‘minima naturalia'” (Boyle, 1666). Boyle is claiming that two corpuscles cannot take up the same space since they are solid entities and thus cannot pass through each other. As stated before, Boyle posited that all qualities observed in substances across nature are a direct result of modification in how corpuscles are arranged, including their number, or their formation. These formations are then put into motion to actually give the created substance function. In this work, Boyle also incorporates a more theological aspect into his corpuscular view, maintaining that God was the one that created substances and motion, and thus indirectly guides corpuscles to create everything that is observable in nature.
Boyle’s purpose in establishing his corpuscular hypothesis was to redefine the work of chemistry. Being a pioneer of chemistry and experimental science as a whole, Boyle hoped to reshape chemistry into the study of the arrangement of corpuscles and how they could be transformed through processes such as distillation. He also treated his hypothesis as a work in progress, saying that “…laying a foundation on which you, and perhaps I, may build a more distinct and explicit theory of qualities than I shall at present try for” (Boyle 1666). His corpuscular hypothesis was indeed later built upon and refined by his contemporaries, including Antione Lavoisier and John Dalton to become the modern atomic theory.
Glossary of Key Terms
- Active Principle: Boyle’s way of describing motion, stated to be the “grand agent” of all physical change. It acts mechanically to divide matter into corpuscles.
- Aristotelian Theory: The ancient natural philosophy, dominant in Boyle’s time, which stated that all matter was composed of the four basic elements: earth, air, fire, and water. Boyle critiqued this for its shifting, unhelpful definitions and lack of experimental proof.
- Corpuscles: The “small particles” that Boyle posited all matter is composed of. When put together in different formations, they form all that is observable.
- Corruption: Boyle’s mechanical term for destruction. It is the loss of a body’s specific arrangement of corpuscles, generating a new substance but not destroying the matter
- Generation: Boyle’s mechanical term for creation. It is not the creation of new matter, but the arrangement of existing corpuscles into a new form.
- Monism: The philosophical idea that all reality could be created from a single substance. Boyle’s hypothesis is a form of monism because it posits that all diverse materials are simply different arrangements of the same single substance (corpuscles).
- Primary Qualities: The inherent, objective properties of the corpuscles themselves, which include their size, shape, and motion.
- Secondary Qualities: The observable qualities of a substance, such as color or taste. Boyle argued these are not fundamental properties, but are a direct result of modification in how corpuscles are arranged, and the further interaction with our senses.
- Tria Prima (Three Principles): The alchemical theory which claims all natural bodies arise from three principles: sulfur, mercury, and salt. Boyle critiqued this theory for its lack of scientific grounding and experimental inconsistency.