In the study of human thought there could hardly be a more fundamental
con- cern than language and reasoning. In the tradition of Western
philosophy, humans are distinguished by their ability to speak and to
think rationally. And language is often considered a prerequisite for
rational thought. If psycholoQists, then, are ever to discover what is
truly human about their species, they will have to discover how language
is produced and understood, and how it plays a role in reasoning and
other forms of rational thought. Within psychology there has been an
imperative to study language and rea- soning together. Since Wundt,
psychologists have succeeded in building a the- oretical foundation for
both language and reasoning. What has become clear from these beginnings
is that the two are inextricably bound to each other. Like the two
players ina chess game, take away one of them and the game no longer
exists. On the one hand, producing and understanding speech re- quires
an intricate process of reasoning. Speakers must rationally choose
sentences that will affect their listeners in ways they intend, and
listen- ers must infer what speakers could conceivably have meant in
selecting the sentences they did. Reasoning, inference, and rational
thought lie at the very center of speaking and listening. On the other
hand, logical reasoning begins with, and is influenced by, the language
in which a problem is stated.