dimly, on the wall opposite, where a strikingly clear but inverted epitome of the world is made to appear.7 Over the course of the late seventeenth century, camera obscuras appeared in a wide variety of models and formats; to the pinhole was added a lens, and to the dark room a mirror and later a semitransparent screen of oiled paper. By the turn of the eighteenth century, the camera obscura had become a familiar sight; in the year of Locke’s death alone, encyclopedist John Harris offered a detailed account of the device for popular use, a “Mr. Marshall” began selling a version of the camera obscura in his shop on Ludgate Hill, and Newton’s Opticks demonstrated its employment in optical experiments.8
The device had its practical applications. When Robert Hooke presented a design for a portable camera obscura to the Royal Society, it was exactly with an eye to its “use to take the draught of a picture of anything.”9 This was not his first; he had previously pitched two such devices, first in 1668, and again in 1680. But his last was his most ambitious. Hooke was trained as a draughtsman, having among other things served as apprentice in the studio of the painter Peter Lely; as his sketchbooks and illustrations attest, he was himself brilliantly accomplished in capturing the outlines of things (see Exhibit 10). The goal of the portable object, as Hooke delivered it, was to unfold the technique of drafting into its components; it was to take the art of design out of the head and put it in a tool. The purpose of Hooke’s “picture box” was explicitly to make possible the accurate depiction of objects in the field by people untrained in the art of drawing, rendering one stage or aspect of the brokerage of images an automatic process.
But the camera obscura had philosophical attractions, too. First, it models the work of the eye, which condenses a world of light into a picture on the retina.10 Several things had to happen for this to be possible. For one, people had to begin thinking of the eye as a lens combined with a receptive surface—cornea and retina. Prior to early seventeenth-century thinkers, including Johannes Kepler and René Descartes, theory was likely to think of the eye as a mere container for an absorptive “vitreous humour”;11 but after Kepler and Descartes, the new science was most apt to think of the eye as an instrument, working by focusing rays of light on its back surface.12 From this shift was developed an epitome theory of vision, that is, the eye as a machine for capturing compact but precise pictures of things; Hooke, for instance, describes the interior globe of the eye as a “microcosm, or a little World,” perfectly answering, point for point, the visual field it confronts. This is quite explicit. “When a Hemisphere of the Heavens is open to its view,” Hooke concludes, the eye “has a Hemisphere within it self.”13 For every point in the field of view, there is a corresponding point in the back of the eye. Locke agreed with Hooke that the critical juncture between mind and world was “far from being a point”; rays of light “strike … on distinct parts of the retina,” where they “paint” a “figure”—the bigness of which Locke is at some trouble to estimate.14 These are theories of vision made possible, as Svetlana Alpers and others have noted, by experiments conducted with the camera obscura. Locke’s theory of optics, like Hooke’s, depended upon practical modeling; in this way, experiments with scopic gadgets affected abstract theories of vision.15
But this is only the first move the camera obscura makes possible, and Hooke’s design, which manages to slice the camera neatly in half while leaving its operator (Hooke himself?) neatly intact, additionally implies the strange doubling that must occur for the object to make epistemological sense. By isolating images from objects, the camera obscura offered a model for the mind separate from matter, in which a metaphorical eye—the “eye of the understanding”—presides over sensory images.16 Locke is quite clear about the similarities between eye and mind; “impressions made on the retina by rays of light” produce isomorphic “ideas in the mind.”17 It is from the senses, Locke therefore insists, that the “white paper” of the mind derives its “vast store,” and all the “endless variety” of ideas that have been “painted on it.”18 Images from the eye fall on a surface in the mind, upon which the judgment or understanding goes to work. From a painting in the eye to a painting in the mind, thinking was a matter of an internal eye consulting its store; henceforth, thinking could be imagined as the mind ranging over its perceptions. Hooke himself, in the same document in which he most fully links the optical camera obscura to the physiology of the eye, describes the mind as just such an open space, with the eye of the soul presiding over its objects (Exhibit 11).19 And so the camera obscura was apprehended as a metaphor virtually simultaneously as it was understood as an ocular gadget; to the extent that it was witnessed as a model for the eye, it was also adopted as material ground for an epistemology. It established, in Jonathan Crary’s account, “categorical relations between interior and exterior, between light source, aperture, and screen, and between observer and representation.” It shifted distinctions between inside and out to an epistemological register. It emerged, in other words, as “a sovereign metaphor for describing the status of an observer.”20
The connections between Hooke, who presented several models of the camera obscura to the Royal Society, and Locke, who may have witnessed one or more of them there, may be strengthened, for they shared a mentor.21 This was Thomas Willis. Willis was a founding member of the Royal Society, but even before his days in London, he was part of the critical Christ Church group of scholars and natural philosophers that at different times included Hooke and Locke. Willis knew the slippery wetware of the brain better than anyone; he had pioneered the difficult surgical techniques making it possible, for the first time, to lay aside the lobes of the brain and penetrate to its delicate, ringlike vascular core. But despite the mess of fat and nerves with which he was left, he clung still to a chamber theory of mentation.22 Embedded in the brain, he surmised, is a “callous body” like a “white Wall.” In his Discourses Concerning the Souls of Brutes, Willis puts the matter this way: “Sent or intromitted by the Passages of the Nerves,” Willis writes, are the “Images or Pictures of all sensible things,” which are made to fall on this callous body.23 For each philosopher, it is as though the optic nerves from retina to ventral cortex carried perfect images, fiber-optic-like, and cast them upon a cartilaginous membrane. This specially textured reception surface, receiving impressions from without, produces “Perception[s],” that is, “Imagination[s] of the thing felt.” Willis, in his own poetic turn of phrase, calls this interior space the “Chamber of the Soul, glased with dioptric Looking-Glasses.”24 With allowances for Willis’s tradecraft, the brain surgeon has here anticipated the poetic image that would turn up in Akenside’s Pleasures of Imagination (Exhibit 3); Akenside surmises a “wide palace” of the brain, where images are staged and rearranged. And, through the mediation of more discrete metaphors—or are they more material gadgets?—Willis’s thoughts would descend directly to a series of similar spaces: Locke’s “dark room,” for instance, or what would become Hooke’s strikingly realized “Repository” of the mind (see Exhibit 11).
Were the drawing of Hooke’s camera obscura more rigorously exact, then, were it to have bisected the man just as neatly as it bisects the beak-like gadget in which he stands, we might have seen a second camera obscura, impossibly miniaturized, at work behind the large eye of the viewer.25 The first is made of ground glass, deal board, and oiled paper; the second is made of a strangely glass-like eye, curved bone, and sensitive membranes. In the first case, the camera obscura is an optical model; in the second, it is a model for mental work. Reproduced on the other side of the eye, invisibly, the camera obscura becomes a figure for judgment or awareness; indeed it becomes a figure that splits judgment from the objects it contemplates, producing consciousness as a tiny eye presiding over images from which it is half-screened. Like Descartes26 and Willis before them, Hooke and Locke differently offer versions of what has more recently been called the “homunculus fallacy”; it is as though a little person were sitting in front of a screen inside the head, watching a picture show on display. Just as the eye offers, in Hooke’s words, a “microcosm, or a little World” of the field of view that confronts it, so, too, this microcosm is put on display for the delectation of the understanding, the
