Along with being a visual method of scientific investigation in its own right, the process of composite photography was often invoked, in the late nineteenth and early twentieth century, as a powerful philosophical metaphor. I investigate an early chapter in the life of this metaphor: its reception and use by the American philosopher, logician and scientist Charles S. Peirce. I show how Peirce's use of composite photography was rooted in his sophisticated philosophical position on the composite process itself, which had been originally developed by Sir Francis Galton in the late 1870s. I highlight substantial differences in the ways Peirce and Galton drew on the composite process to advance broader epistemological claims -especially claims concerning the nature and reliability of scientific generalisations. I argue that Peirce and Galton's respective approaches to the issue of generalisation and generality condense deeper epistemological tensions that deserve renewed philosophical consideration. I conclude by arguing that the material dimension of photography as a mode of representation in its own right, and in particular the limitations of the photographic process as an "objective" mode of representation, were ultimately of crucial importance for the ways in which Peirce adopted and articulated the metaphor of composite photography in his philosophical works.