The Lagoon: How Aristotle Invented Science

by Armand Marie Leroi

ORGANON MEANS ‘TOOL’ or ‘instrument’.* It’s the title often given to six of Aristotle’s books. It’s an apt one for they are tools for the production of knowledge. One of these books, the Posterior Analytics, contains his scientific method. Aristotle distinguishes the rules for debating opinions from the rules for constructing scientific explanations. The first he called ‘dialectic’, the latter ‘demonstration’ (the Greek is apodeixis). By ‘demonstration’ he means exactly what a modern scientist means when he says, ‘we have demonstrated that A is the cause of B’ – that is, he and his collaborators have shown that the presence of A is a necessary and sufficient condition for B. He had a high notion of the power of scientific demonstrations: he thought that they delivered truth. That’s because they are the products of logical operations. Aristotle invented the theory of inferential logic known as his syllogistic. It was his greatest technical achievement and dominated the subject for millennia even if it was incomplete and, in parts, wrong. His syllogistic aimed to deduce new conclusions from established premises where the premises are propositions that contain a subject and a predicate, e.g. ‘All octopuses [subject] are eight legged [predicate].’ To analyse such statements he invented a formalism that substituted letters for the terms, e.g. ‘All A are B.’ This formalism allowed him to speak generally of all propositions of a given form, manipulate them and derive the many res...