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Charles Peirce believed keenly in the reality of laws and universals. He claimed that despite modern naturalistic philosophy’s self-conception as triumphing over a dessicated Aristotelianism, a view of universals closest to that of Duns Scotus was “the philosophy which is best to harmonize with physical science” (1). Much high-quality scholarship outlining this aspect of Peirce’s thought already exists. However, this fine book lucidly systematizes it in a new synthetic approach to the problem that revives natural links between realism and a general theory of inquiry. For all modern realism’s claims to be ontologically committed to mind-independent entities, it has largely severed itself from a philosophical account of how to determine independent existence in particular cases, instead relying on natural science or “intuition.” Forster argues that this philosophical lacuna itself constitutes a form of nominalism; thus, realism in its deepest sense may be understood as explanatory ambition.
The book begins by outlining why Peirce saw nominalism as such a threat. It “limits the scope and authority of reason and … yields far too much to scepticism in science, ethics and religion” (7). By contrast, Peirce ambitiously seeks “an ultimate impartial and binding basis for the organization of human life” (12). A great interest of this book is in tackling head-on what many contemporary philosophers have filed in the too-hard basket.
The main argument begins with an account of “the science of inquiry.” Forster outlines five requirements: it must be a priori, formal, universal, necessary, and normative, and must license metaphysical conclusions (20). This obviously means that it cannot be a natural science. But neither can it be grounded in appeals to pure reason, as these amount to reliance on intuition, which cannot “distinguish principles that are truly self-evident from those that only seem to be” (25). But natural or a priori science—what other option could there be? One of the great excitements of Peirce’s thought is how it frequently breaks timeworn dichotomies with a third alternative. As a new foundation for the science of inquiry, Forster offers diagrammatic reasoning. Such reasoning is experimental, and thus more than intuition-mongering, yet there can be no mismatch between the way things are and the way they are represented to be, since the relations among elements of diagrams are the very objects of study. [End Page 137]
In chapter 3, Forster uses diagrammatic reasoning to argue that nominalism cannot give an adequate account of continuity, for general concepts do not refer to collections of individuals but manifolds of actual and possible entities “welded together” (this issue is arguably insufficiently studied by metaphysicians). Next, Forster notes that the nominalist might claim that true continuity is a coherent hypothesis that cannot be verified, as the world consists solely of individuals. But he argues that Peirce’s pragmatic maxim challenges this, teaching that the meaning of a term is a general pattern of effects, expressed in hypothetical conditionals.
But why should we use the pragmatic maxim? Peirce worked long and inconclusively in his later years on a “proof of pragmatism,” which Forster claims can be reconstructed from his theory of symbols. It holds, roughly, that insofar as symbols are interpretable they require the interpreter to gauge their implications, which must be empirically accessible effects. This argument has many steps and I am not convinced Forster has nailed down every possible counterargument, but it is a worthy attempt.
The nominalist will protest that this epistemological story does not yet require metaphysically real universals. In his mature work Peirce argued that universals may be directly perceived. Appreciating this requires an analysis of perception considerably more sophisticated than today’s British empiricist legacy. Whereas for Hume the percept (impression) is directly copied into the sign (idea), for Peirce this approach “overlooks enormous differences between the feeling of, say, a yellow quale and the term ‘yellow’ as it occurs in a judgment,” whose meaning “is dependent on the object it represents and its effects on interpreters” (114). Incorporating such judgments turns the meaning of...