Through a detailed analysis of the various modes of argumentation employed by Aristotle throughout his natural scientific works, I aim to contribute to the growing scholarship on the relation between Aristotle’s theory of science and his actual scientific practice. I challenge the standard reading of Aristotle as a methodological empiricist and show that he permits a variety of non-empirical arguments to support controversial theses in properly scientific contexts. Specifically, I examine his use of logical (logikôs) argumentation in the discussion of (...) mule sterility in Generation of Animals II 8, rational (kata ton logon) argumentation in his discussion of cardiocentrism throughout the biological works, and the method of division in Posterior Analytics II 13. (shrink)