From Discursive Practice to Logic? Remarks on Logical Expressivism

  • Rodger Kibble Department of Computing, Goldsmiths, University of London


This paper investigates Robert Brandom's programme of logical expressivism and in the process
attempts to clarify his use of the term practice, by means of a comparison with the works of sociologist
and anthropologist Pierre Bourdieu. The key claim of logical expressivisim is the idea
that logical terms serve to make explicit the inferential relations between statements which already
hold implicitly in a discursive practice that lacks such terms in its vocabulary. Along with this, it
is claimed that the formal validity of an argument is derivative on so-called material inference, in
that an inference is taken to be logically valid only if it is a materially good inference and cannot
be made into a bad inference by substituting nonlogical for nonlogical vocabulary in its premises
and conclusion. We note that no systematic account of logical validity employing this substitutional
method has been offered to date; rather, proposals by e.g. Lance and Kremer, Piwek, Kibble
and Brandom himself have followed the more conventional path of developing a formally defined
system which is informally associated with natural language examples. We suggest a number of refinements
to Brandom’s account of conditionals and of validity, supported by analysis of linguistic
examples including material from the SNLI and MultiNLI corpora and a review of relevant literature.
The analysis suggests that Brandom’s expressivist programme faces formidable challenges
once exposed to a wide range of linguistic data, and may not in fact be realisable owing to the
pervasive context-dependence of linguistic expressions, including 'logical' vocabulary. A further
claim of this paper is that a purely assertional practice may not provide an adequate basis for conditional
reasoning, but that a more promising route is provided by the introduction of imperatives,
as in so-called "pseudo-imperatives" such as "Get individuals to invest their time and the funding
will follow". We conclude the resulting dialogical analysis of conditional reasoning is faithful to
Brandom's Sellarsian intuition of linguistic practice as a game of giving and asking for reasons, and
conjecture that language is best analysed not as a system of rules but as a Wittgensteinian repertoire
of evolving micro-practices.