Thomas Reid and the Problem of Secondary Qualities by Christopher A. Shrock (review)

Philosophers from the modern age and current philosophers share some common concerns. One is whether the ordinary objects of human perception—the objects humans see, hear, feel, taste, and smell—exist independently of our perception of them in a shared, stable, spatially-localized environment that also exists independently of perception. Another is whether a particular range of properties—colors, flavors, odors, sounds, feels—are (a) properties of the ordinary objects of human perception, (b) relations whose relata are properties of ordinary objects and types of typical human experiences, or (c) properties of, or identical with, types of typical human experiences.

Because both modern and current philosophers have these concerns, one way to investigate these topics is to put the two in conversation with one another. Shrock's book does so in a unique way. Part I begins with direct realism—one answer to the question of whether the ordinary objects of perception exist independently of perception. Direct realism is introduced as one of three alternatives, each of which has a modern representative. We learn that Berkeley and Hume are idealists and that each privileges "cool reason" over perceptual experience (10). We learn that idealism holds that ordinary objects are ideas in our minds and that Hume and Berkeley demand that we reject our irresistible belief in the permanence and subject-independence of ordinary things. Locke represents indirect realism; and we are told that he, Hume, and Berkeley are motivated to hold their positions "in order to solve theoretical problems with illusions and hallucinations" (18). Reid represents direct realism, which is introduced not by the extensive literature on Reid's direct realism, but by recent work from Michael Huemer and Noah Lemos. Direct realism is defended by assessing the views attributed to Locke, Berkeley, and Hume as implausible, using G. E. Moore, P. F. Strawson, John Foster, Howard Robinson, and other twentieth- and twenty-first-century philosophers.

The remainder of part I uses a similar method. As the title suggests, Reid, along with other modern philosophers, struggled with Locke's distinction between primary and secondary qualities. And many Reid scholars have recognized and addressed the particular problem secondary qualities pose for Reid's direct realism. Schrock identifies the problem of secondary qualities as one variant of the argument from illusion, and provides brief assessments of twentieth- and twenty-first-century views that engage these problems, from adverbialism and behaviorism, to disjunctivism. He concludes that a direct realist must commit herself to the position that secondary qualities are scientific properties of objects if she is to avoid the problem—a position he goes on to identify with Reid in part II.

Part II promises to cover Reid's views on "the conceptual nature of perception, the contingent connection between sensations and perceptions, and the role of sensations as natural signs"—topics at the core of Reid scholarship for the last thirty years (54). Shrock acknowledges a portion of this literature while focusing on his own account of these matters, leaving chapter 6 and part III for "interpretive minutiae" (54). Shrock argues that Reid recognizes no metaphysical distinction between primary and secondary qualities: both are "physical-causal, scientific properties … possessed by physical objects" (89). In other words, there is no primary-secondary quality distinction for Shrock's Reid, metaphysically speaking, which puts Reid in a unique position relative to "the traditional primary/secondary guru John Locke" whom we are told takes "secondary qualities to be mental" (66). Reid holds that perception is direct; secondary properties are scientific properties of the objects of perception (i.e. real); the problem of secondary qualities for direct realism is solved.

Reid does draw an epistemic distinction, however, between qualities humans conceive directly and distinctly in the course of perception (primary qualities), and those that humans conceive relatively and obscurely in the course of perception (secondary qualities), which Shrock recognizes as the only primary-secondary quality distinction in Reid. We conceive of...