Abstract

Those enlightened philosophers of physics acknowledging some manner of descent from Kant’s ‘Copernican Revolution’ have long found encouragement and inspiration in the writings of Roberto Torretti. In this tribute, I focus on his “perspective on Kant’s perspective on objectivity” (2008), a short but highly stimulating attempt to extract the essential core of the Kantian doctrine that ‘objects of knowledge’ are constituted, not given, or with Roberto’s inimitable pungency, that “objectivity is an achievement, not a gift.” That essential core Roberto locates in the Kantian notion of apperception, or self-activity, manifested in cognition in the idea of combination (Verbindung) or composition, which, Kant tells us, “among all ideas … is the one that is not given through objects, but can only be performed by the subject itself, because it is an act of self-activity” (B 130). I first rehearse Roberto’s proposal for how an imaginative interplay between sensibility and understanding can be fashioned via the productive imagination or power of reflective judgment (of the third Critique). In this way, the notion of composition in general, unfettered from needless period constraints issuing in “pure forms of sensibility” and “pure concepts of the understanding”, can be seen as the intellectual motor for the “free creation” of concepts celebrated by Einstein and others, furnishing structural scaffolding required to articulate and display physical objects and processes, a conceptual panoply that “cannot be fished out of the stream of impressions”. Roberto emphasizes that historical case studies are needed to evaluate his proposal, suggesting one himself, the continuous conceptual development inaugurated by Riemann’s Habilitätionsschrift (1854) resulting, some hundred years later, in the fiber bundle formalism of modern differential geometry and topology. I sketch a related suggestion, that the gauge groups of modern particle physics are the outcome of a similar line of conceptual advance, a structural scaffolding saving the phenomena of high-energy experiment within the framework of ‘effective field theory.’