The Evolution of Logic

Our ability to reason by logic is exceptional in nature. We are the reasoning animal. Like all animals, we evolved during a long natural process. Unlike other animals, we developed sophisticated minds and a complex language that contains logical structure. Yet it is remarkably unclear how logic became part of nature. Where does logic come from? The goal of this project is to understand the origins of the human capacity for logical reasoning. Merging philosophical logic and evolutionary linguistics, the general hypothesis is that logic evolved to support social interactions and efficient communication. The particular focus will be on the evolution of quantificational reasoning, which is key to the ability to generalize and to count. There are three parts to this project. First, to explain what we have: the grammar of natural language includes simple words to express quantification ('every', 'always'). What were the conditions for the emergence of the cognitive abilities thereby manifested in speech? Second, to explain what we don't have: no language of the world includes simple words for concepts such as 'not every' and 'not always'. These quantifiers have to be expressed compositionally, by combining simpler building blocks ('not' with 'every' and 'often'). This is not a coincidence: the difference between what can be expressed as a lexical item and what must be expressed by composition is the difference between what can be memorized by the child acquiring a language, and what must be generated by the grammatical engine. Third, to explain how it all comes together: is logic the result of natural selection, cultural inheritance, or something else? The study of logic from an evolutionary perspective will provide a window into the origins of the human mind, with a wide-ranging impact on philosophy and neighboring disciplines.