What To Do With Seventeenth-Century Natural Philosophy? A Taxonomic Problem

The issue at stake

According to our history books, modern philosophy and modern science were both born in the seventeenth century. If this was merely a matter of temporal coincidence, there would be nothing remarkable about it. But the two phenomena appear to be connected: historians of philosophy and historians of science do not only look to the same time period for the birth date of their respective modern histories, but they often look to the same people and in some cases even to the same texts.

What are the implications of this overlap? If the history of philosophy and the history of science could be so completely mapped upon each other as to appear as one identical enterprise, this would constitute a lesser problem. It would then suffice to explain how it came that two enterprises that today are quite distinct pursuits joined hands for a certain period. But the problem is much more vexing than that: while it is generally understood that the redefinition of philosophy and the birth of modern scientific methods are linked phenomena, no one has ever taken them to constitute identical enterprises. At the same time, the type of link between the two phenomena continues to be debated. Must we assume the existence of an essential bond between the two, or did the development in one field trigger a revolution in the other?

One of the main keys to the understanding of the nature of this puzzle lies with "natural philosophy" and with the enormous growth and reorientation of this discipline in the seventeenth century. "Natural philosophy" had for centuries been a bookish discipline "without nature" (John Murdoch 1982) and, while being "empiricist" in nature, had proceeded "without observations" (Edward Grant 2001). It had sought solutions to conceptual riddles and seeming inconsistencies found primarily in Aristotle's libri naturales and in the commentary tradition these texts had engendered. When speaking of "medieval science," careful historians therefore distinguish between the philosophical and propedeutic discipline of natural philosophy, on the one hand, and those various other activities that must be mentioned among the precursors of modern scientific disciplines, notably medicine; certain techniques in the domains of alchemy or metallurgy; the quadrivial disciplines and notably astronomy; or the mixed sciences and specifically optics.

With regard to the Middle Ages and the Renaissance, then, it is not too difficult to distinguish the explicitly "speculative" and "contemplative" discipline of philosophia naturalis or physica from those other activities. However, the picture changes fundamentally in the seventeenth century. With the introduction of experimental and mathematical approaches to the study of natural phenomena, traditional differences between speculative thought and practice, literary study and applied labor became blurred. All kinds of non-scholastic activities came to insert themselves into the old scholastic domain of philosophia naturalis or physica, which in the process turned into a mathematical, chemical, medical, and generally empirical discipline. The confusing consequence was that everyone who was concerned with some aspect or other of the natural world came to consider himself ipso facto a "philosopher." This immense extension of the field of philosophical activity explains also why instruments such as telescopes, prisms, or vacuum pumps came to be regarded as "philosophical instruments." Although this redefinition of the scope of philosophy to cover experimentation and observation could be (and sometimes was) celebrated as a return to the original Greek spirit of the philosophical enterprise, it obviously far exceeded the definitional boundaries of both what had previously been called "philosophy" and what we nowadays understand by this term.

This situation confronts the modern historian with a series of difficulties and not least with a problem of taxonomy. By calling "philosophical" much of what to us looks like "science," the seventeenth century appears to snatch away from historians of science almost all that is of interest to them about this period. At the same time, it forces the historian...