Extending Intensions: Exploring Deleuze and Guattari's Critique of Formal Logic in the Case of Intensional Logics

In What is Philosophy?, Deleuze and Guattari critique the relationship between formal logic and philosophy. They argue that since philosophy is the creation of concepts that are intensional, and formal logic reduces concepts to their extension, formal logic then has no special providence to decide philosophical questions. This may strike the logic-inclined philosopher as outdated given that there are now formal intensional logics designed to model meaning rather than reference. However, it will be shown that these logics too fail to express the concept in a way that preserves its philosophical import. Doing so requires contrasting Deleuze and Guattari's account of the concept with Frege's to show how the latter persists even in intensional logics in the form of mathematical functions that are ultimately referential. This then results in support for Deleuze and Guattari's claim that formal logic is a useful tool, but that it is incapable of adjudicating philosophical disputes.