Single Review on past events

In his presentation on “Semantic Structure and the Structure of Rationality” Associated Fellow Brendan Balcerak Jackson gave an exciting insight into his philosophical studies of linguistic meaning. “One traditional aim of philosophers is to understand the nature of thought and rationality, in part by uncovering rules of rationality that govern good or correct reasoning”, he defined. Rules of rationality describe relations among psychological states, e.g. belief, intention, preference etc., but they also concern the relations of mental states besides beliefs.  To illustrate the rules of rationality he used one simple example: When you know that your keys are either on your desk or in your coat pocket, and you determine that they are not on your desk, then you conclude that they must be in your coat pocket.

We display rationality in our use of language as well. He stated that “competence with a natural language involves a cluster of capacities to engage in linguistic reasoning – reasoning with and about expressions of the language”. For example, we can infer the meanings of new words from linguistic context, and we can employ words learned in one linguistic context in various other kinds of linguistic context.

Every natural language has a semantic structure, by virtue of which the language is systematic, unbounded and compositional. Systematicity means that speakers who grasp a given sentence can grasp others constructed in the same way out of the same vocabulary. Unboundedness means that there is no upper limit on how many distinct sentences speakers can grasp. And compositionality says that the meaning of a complex expression is determined by the meanings of its parts and the way it is constructed. A compositional semantic theory includes two components: a lexicon that assigns meanings to the basic expressions of the language, and a set of composition rules that specify how the meanings of complex expressions are determined, in terms of the basic meanings given in the lexicon, and on the basis of how they are constructed.

The philosopher described the relationship between semantic structure and understanding by proposing the Reflection Thesis: “The composition rules for a given language represent rules of rationality that govern the linguistic reasoning of speakers of the language.” The Reflection Thesis provides an alternative to the dominant “tacit knowledge” approach to linguistic understanding, as the dominant approach treats composition rules as part of the information at speakers’ disposal. Speakers reason about this information in accordance with the same general (topic-neutral) rules of rationality they use in other domains. But this information is only tacitly known: available for certain reasoning tasks but not others.

Brendan Balcerak Jackson further argued: “If the Reflection Thesis is correct, then composition rules reflect constraints on linguistic reasoning. Speakers need not know such rules, not even tacitly. They represent correct ways of handling the knowledge speakers have about the language (e.g. from the lexicon).” He concluded his talk by saying that the Reflection Thesis also suggests new approaches to some of the general philosophical questions about rationality, as it implies that not all rules of rationality are formal and topic-neutral; at least some rules govern specific sorts of reasoning in circumscribed domains. Such substantive (domain-specific) rules do more than merely define what counts as “reasoning,” and these rules may be grounded in facts about how the speaker’s psychology functions in normal/ideal conditions.”