Psychophysiological approach to the Liar paradox: Jean Buridan’s virtual entailment principle put to the test
This article presents an empirical examination of the consequences of the virtual entailment principle proposed by Jean Buridan to resolve the Liar paradox. This principle states that every sentence in natural language implicitly asserts its own truth. Adopting this principle means that the Liar sentence is not paradoxical but false, because its content is contradictory to what is virtually implied. As a result, humans should perceive the Liar sentence the same way as any other false sentence. This solution to the Liar paradox received criticism for making ad hoc claims about the natural language. However, thanks to modern advancements in psychophysiology, it became possible to empirically investigate if the human brain really perceives the Liar sentence like a false sentence. We designed and conducted an experiment to examine brain activity in response to true sentences, false sentences and self-referential sentences (including the Liar and the Truthteller). Our results provide support for the Buridan’s hypothesis and show that the Liar sentence is processed by the human brain identically to false sentences, while the Truthteller sentence is perceived identically to true sentences. This agrees with predictions derived from the virtual entailment principle and supports the idea that humans think with the logic of truth—a logic for which the truth is a designated value of its adequate semantics.
KeywordsLiar paradox Jean Buridan Entailment Relativism ERP N400 Experimental philosophy Neurophilosophy
We would like to thank Professor Hanna Bednarek (Department of Cognitive Psychology, SWPS University, Warsaw) who helped us with obtaining the approval of the Ethical Committee for the experiment, and Professor Aneta Brzezicka (Department of Psychophysiology of Cognitive Processes, SWPS University, Warsaw) who allowed us to use the EEG laboratory.
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