Type Logical Grammar: Categorical Logic of Signs Book

Dixon proposes that Eldredge and Gould's punctuated equilibrium can be used to explain change in language on a macro-scale: periods of equilibrium, where languages do not qualitatively change are described by change through diffusion; punctuations, where several new languages suddenly appear or languages disappear, are described by the family-tree model.

The book shines in its criticism of the family-tree model and its overuse. Especially, chapters 3 and 4 on language diffusion and the family-tree model show that similarities between languages that are easily explainable by these being in constant contact with each other (diffusion) have been attributed, mostly likely mistakenly, to a common origin. Also useful is the criticism of formalism, including Chomsky's theories, and its methods in linguistics.

Dixon, however, quite generous with citations for most of the book, states a series of propositions (especially in the crucial chapter on modes of change in language) that leave it to the reader to figure out if these are, for example, mechanisms of change that have been rigorously proven in the field or just suppositions on his part. Perhaps, as with the change from ergative to accusative in a language, there is a wealth of evidence of all or most cases in a language appearing around the same time, but it is a shame he chooses to thoroughly justify only the former. As well, he sometimes gives explanations of exceptions to rules he posits, and how these are either insignificant or not actually exceptions; sometimes he merely mentions the existence of exceptions. The reader will have to look elsewhere to effectively assess his theory.

Another important gap is his theory of the origin of language: if one says conceptual categories developed first and only afterwards came language, some kind of justification must be given as to how thought can exist without language or at the very least a reference to another's position in that debate.

A minor (in the context of what he is trying to prove) problem: Dixon seems to have a superficial understanding of colonialism and how hierarchical societies "spread" their way of organizing themselves, leaving him to say that missionaries that introduced a game of UNO to a community in the Amazon led people to become competitive and leave their egalitarianism.