'Natures' and 'Laws': The making of the concept of law of nature - Robert Grosseteste (c. 1168-1253) and Roger Bacon (1214/1220-1292)

•In the Thirteenth century, Forms and laws were coherently used in theories of natural causation.•An explanation by form can conform to explanation by law provided that the forms inhere in or issued by every material substance.•By detaching the forms from the particulars of each substance Grosseteste and Bacon turned their conditional necessity absolute.•The common forms addressed by Grosseteste and Bacon are the first building blocks of the idea of the homogeneity of matter.•Bacon turned external causality into an exemplar of natural action. He thus detached the explanatory principle from matter.

Contemporary scholars set the Greek conception of an immanent natural order in opposition to the seventeenth century mechanistic conception of extrinsic laws imposed upon nature from without. By contrast, we argue that in the process of making the concept of law of nature, forms and laws were coherently used in theories of natural causation. We submit that such a combination can be found in the thirteenth century. The heroes of our claim are Robert Grosseteste who turned the idea of corporeal form into the common feature of matter, and Roger Bacon who described the effects of that common feature. Bacon detached the explanatory principle from matter and rendered it independent and therefore external to natural substances. Our plausibility argument, anchored in close reading of the relevant texts, facilitates a coherent conception of both 'natures' and 'laws'.