I was drawn to Cambridge Pragmatism: From Peirce and James to Ramsey and Wittgenstein by Cheryl Misak because it brings together subjective probability and C. S. Peirce’s pragmatism, two lines of thought I admire but whose relationship to one another was a mystery to me. Misak is a foremost authority on Peirce and pragmatism whose many books and articles are written with a clarity that makes them accessible to someone trained as an archaeologist, rather than a philosopher.

My admiration of subjective probability goes back more than 25 years, and comes from habits acquired during the practice of Bayesian calibration of archaeological radiocarbon dates. Early on, I ran across situations where the prior information of the Bayesian chronological model improved, often markedly, both the accuracy and precision of the date estimate. This was an important discovery for my work in Hawaiʻi where the uncertainty in radiocarbon dating due to Industrial Revolution’s use of coal power, which pumped “dead” carbon into the atmosphere and altered the global radiocarbon balance, makes the last quarter of the archaeological sequence almost impossible to date precisely without the addition of the prior information made possible by Bayesian calibration. Later on, I realized that Bayesian chronological models could be constructed to keep an analysis from running off the rails, providing what my colleague Tim Rieth calls “bookends” that keep the estimate from straying too early or too late. The ad hoc methods used by many archaeologists in Hawaiʻi lack this useful property and, indeed, many of their analyses have run silently off the rails. My experience has led me to believe subjective probabilities are good for archaeological thinking. The tie in to Misak’s book is that the Ramsey of its subtitle is Frank Plumpton Ramsey, who laid the mathematical foundations of subjective probability at Cambridge in the 1920s. I was keen to know what Ramsey made of pragmatism.

My admiration of Peirce and pragmatism is more recent. I’d run across Peirce’s name when Per Hage and Frank Harary cited his work on the logic of relations in Structural Models in Anthropology and Exchange in Oceania: A Graph Theoretic Analysis. But it wasn’t until I read a conference paper by the French archaeologist François Djindjian that I was stimulated to read Peirce’s two essays, “How to Make Our Ideas Clear” and “The Fixation of Belief.” Peirce’s analysis of inquiry as transforming doubt into belief through a process that involved abduction, deduction, and induction was an eye-opener for me. When I was in graduate school, New Archaeologists were arguing that the inductive reasoning used by culture historians was inferior to the deductive reasoning they championed. Although I wasn’t convinced one was better than the other, I thought the two were somehow antithetical and it hadn’t occurred to me they might be complementary in the way Peirce explained so clearly.

The mystery about the relationship of subjective probability and pragmatism started many years ago, when I read somewhere (that I’ve now forgotten and am too busy to track down) that Peirce discounted subjective probability and was a strong advocate of objective probability. As an undergraduate, I took a course on probability theory where I learned a bit about the acrimonious debates between frequentists and subjectivists and I was perplexed to imagine that Peirce and I appeared to be on opposite sides of the debate. Peirce was a scientist deeply involved with issues of measurement—for 32 years he worked for the U.S. Coast and Geodetic Survey making careful measurements of the intensity of the earth’s gravitational field using pendulums that he designed and built—and I felt certain that the experience I’d had with Bayesian calibration was of a kind that Peirce would have recognized and appreciated.

Misak’s book solved my mystery. Peirce was not a staunch objectivist, but recognized both objective and subjective probability. However, he believed that objective probability is fundamental because it is determined by facts. In his view, the degrees of belief calculated by the subjectivist must be keyed to objective probability, so that one’s beliefs correspond closely to facts. Ramsey credits his reading of Peirce with stimulating his interest in probability, an interest that led him to formulate the mathematical basis of subjective probability. In a sense then, the Bayesian calibration that I practice in archaeology counts Peirce and pragmatism among its intellectual ancestors.