1.1.1. Logic
Logic is a study of reasoning. However, it does not concern the ways and means by which people actually reason—as psychology does—but rather the sorts of reasoning that count as good. So, while a psychologist is interested as much in cases where people get things wrong as in cases where they get them right, a logician is interested instead in drawing the line between good and bad reasoning without attempting to explain how cases of either sort come about.
Another way of making this distinction between logic and psychology is to say that, in logic, the point of view on reasoning is internal: it is a study from the inside
in a certain sense. As we study reasoning in this way, we will be interested in the norms of reasoning—the rules that reasoners feel bound by, the ideals they strive to reach—rather than the mixed success we observe when we look from outside on their efforts to put norms of reasoning into practice.
This makes logic much like the study of grammar. A linguist studying the grammar of a language will be interested in the sort of things people actually say, but chiefly as evidence of the ways they think words ought to be put together. So, although linguists do not attempt to lay down the rules of grammar for others and see their task as one of description rather than prescription, what they attempt to describe are the (largely unconscious) rules on the basis of which the speakers of a language judge whether utterances are grammatical.
Indeed, one way of understanding logical norms suggests that there is more than an analogy between logic and the study of language. However ineffable language itself may sometimes seem, it is vastly more concrete than thought and it has always served logicians as a tool in their study of reasoning. In the 20th century it acquired an even greater significance because the traditional view of the relation between thought and language (according to which thought is independent of language and language acquires its significance as the expression of thought) came to be reversed, and thought was seen to derive its significance from the possibility of linguistic expression. As a result, the norms of thought have often been seen to derive from the norms of language, specifically from rules governing certain aspects of meaning. This view is not uncontroversial, but we will see in 1.2 that there is a way of describing the norms of reasoning that makes it quite natural to see them as resting on norms of language.