The recent wave of data on exoplanets lends support to METI ventures (Messaging to Extra-Terrestrial Intelligence), insofar as the more exoplanets we find, the more likely it is that “exominds” await our messages. Yet, despite these astronomical advances, there are presently no well-confirmed tests against which to check the design of interstellar messages. In the meantime, the best we can do is distance ourselves from terracentric assumptions. There is no reason, for example, to assume that all inferential abilities are language-like. (...) With that in mind, I argue that logical reasoning does not have to be couched in symbolic notation. In diagrammatic reasoning, inferences are underwritten, not by rules, but by transformations of self-same qualitative signs. I use the Existential Graphs of C. S. Peirce to show this. Since diagrams are less dependent on convention and might even be generalized to cover non-visual senses, I argue that METI researchers should add some form of diagrammatic representations to their repertoire. Doing so can shed light, not just on alien minds, but on the deepest structures of reasoning itself. (shrink)

Since Peirce defined the first operators for three-valued logic, it is usually assumed that he rejected the principle of bivalence. However, I argue that, because bivalence is a principle, the strategy used by Peirce to defend logical principles can be used to defend bivalence. Construing logic as the study of substitutions of equivalent representations, Peirce showed that some patterns of substitution get realized in the very act of questioning them. While I recognize that we can devise non-classical notations, I argue (...) that, when we make claims about those notations, we inevitably get saddled with bivalent commitments. I present several simple inferences to show this. The argument that results from those examples is ‘pragmatic’, because the inevitability of the principle is revealed in use (not mention); and it is ‘semiotic’, because this revelation happens in the use of signs. (shrink)

Mercier and Sperber (MS) have ventured to undermine an age-old assumption in logic, namely the presence of premise-conclusion structures, in favor of two novel claims: that reasoning is an evolutionary product of a reason-intuiting module in the mind, and that theories of logic teach next to nothing about the mechanisms of how inferences are drawn in that module. The present paper begs to differ: logic is indispensable in formulating conceptions of cognitive elements of reasoning, and MS is no less exempt (...) from taking notice of premise-conclusion structures than the commonplace theories of reasoning are. Our counterclaim is realized in terms of diagrammatic reasoning dating back to Charles Peirce’s pragmaticism. The upshot is that pragmatist logic restores the premise-conclusion structures in argumentation, supplants reason-intuition module with logical content, and validates good reasoning as an indispensable resource evident to all rational minds that claim ownership of reason and understanding. (shrink)