Words and Rules: The Ingredients of Language is a 1999 popular linguistics book by Steven Pinker about regular and irregular verbs. "Words and rules" is a theory that has been predominantly developed by Pinker. It has been popularly contextualized within the so-called "Past-Tense Debate," which was sparked by Rumelhart and McClelland's 1986 connectionist model of the production of regular and irregular verbs. In essence, the Words and Rules theory states that past-tense forms of verbs arise from both declarative memory (as words) and procedural systems (from rules). Source: Wikipedia (en)