The Two Scientific Methods of the Discourse on Method

Aaron Spink

University of South Florida

In this essay I argue that the most common strategy for interpreting the connection between Descartes’ method in the Discourse on Method and the examples appended to that work is misguided. The received view is that the method of Descartes' Discourse is found primarily in part II, where he gives four general rules. Further, many commentators have sought to establish a connection to Descartes’ earlier work, the Regulae. An overemphasis on the four rules as the totality of Descartes’ method results in a gross historical confusion: Descartes is seen as presenting a method that, by all accounts, is not followed in his subsequent works. However, I argue that by taking a detailed look at Descartes’ correspondence both before and immediately following the publication of the Discourse, it becomes clear that instead of looking backward to the Regulae (a document never published in Descartes’ lifetime nor mentioned in his correspondence), we should instead look to the three essays that originally accompanied the Discourse: the Dioptrics, Meteors, and Geometry. The problem thus becomes answering how we can square the method of the Discourse with the method actually found in the three essays, which he claims should serve as a demonstration of that method. To this end, I propose that Descartes gives us not one, but two methods in the Discourse. The first, presented as the four rules in part II, and another presented in the often-neglected part VI. The four rules of part II must be seen as a method to be used to generate only the general principles of philosophy, which will later be used to guide experience and experiments. Since Descartes intentionally refuses to give these principles in the Discourse or essays, it is not surprising to find no instance of this method being used. However, what we find in part VI of the Discourse is a brief but instructive order for conducting experiments and collecting observational data—in other words, an experimental method. It is this method presented in part VI that will lead us to the many contingent truths nature can reveal to us. Far from being an armchair scientist, Descartes presents himself as an avid experimentalist where many particular truths of nature are accepted as wholly obscure to reason unless aided by experience and experiment. The fruits of seeing Descartes as presenting two methods—one for general truths and one for particular truths—are innumerable. With this interpretation in mind, we can make sense of why Descartes thought the Discourse did not present his full method; namely, this is because he never gives us a detailed explanation of how the two methods are supposed to interact, which they surely should. Further, the essays no longer present such a dramatic disconnect from the Discourse. Instead, we can see the experimental method applied explicitly throughout. Lastly, the experimentalist elements of Descartes’ correspondence come to the fore and find a very pointed expression in the Discourse.