Richard Zach

In early 1909, Charles S. Peirce conducted a series of experiments with three-valued logic, anticipating the pioneering work of Jan Łukasiewicz and Emil Post by ten years. These experiments are entirely contained within six or seven pages of Peirce's Logic Notebook. Due to the work of Atwell Turquette, the formalisms contained in those pages are relatively well understood. What is less understood are Peirce's philosophical reasons for conducting those experiments. His explanation of the need for his "triadic" logic is very brief, taking up little more than a single short page in the Notebook. Here he gives us two clues about his motivations, one connected to modal notions and one to his views on continuity. There are two previous accounts of the philosophical motivations behind triadic logic, due to Max Fisch and Turquette, and to Robert Lane. In this paper, I re-evaluate those views and connect the two clues to Peirce's hypothetical cosmology. I argue that in conducting his three-valued experiments, Peirce was trying to create a logic to capture his notion of the evolving universe.

An argument going back to Russell shows that the view that propositions are structured is inconsistent in standard type theories. Here, it is shown that such type theories may nevertheless provide entities which can serve as proxies for structured propositions. As an illustration, such proxies are applied to the case of grounding, as standard views of grounding require a degree of propositional structure which suffices for a version of Russell’s argument. While this application solves some of the problems grounding faces, it introduces problematic limitations: it becomes impossible to quantify unrestrictedly over the relata of ground. The proposed proxies may thus not save grounding, but they shed light on what exactly Russell’s argument does and does not show.

When should you engage with difficult arguments against your cherished controversial beliefs? The primary conclusion of this book is that your obligations to engage with counterarguments are more limited than is often thought. In some standard situations, you shouldn't engage with difficult counterarguments and, if you do, you shouldn't engage with them open-mindedly. This conclusion runs counter to aspects of the Millian political tradition and political liberalism, as well as what people working in informal logic tend to say about argumentation. Not all misleading arguments wear their flaws on their sleeve. Each step of a misleading argument might seem compelling and you might not be able to figure out what's wrong with it. Still, even if you can't figure out what's wrong with an argument, you can know that it's misleading. One way to know that an argument is misleading is, counterintuitively, to lack expertise in the methods and evidence-types employed by the argument. When you know that a counterargument is misleading, you shouldn't engage with it open-mindedly and sometimes shouldn't engage with it at all. You shouldn't engage open-mindedly because you shouldn't be willing to reduce your confidence in response to arguments you know are misleading. And you sometimes shouldn't engage closed-mindedly, because to do so can be manipulative or ineffective. In making this case, Jeremy Fantl discusses echo chambers and group polarization, the importance in academic writing of a sympathetic case for the opposition, the epistemology of disagreement, the account of open-mindedness, and invitations to problematic academic speakers.