What is an act of thinking beyond the traditional image of thought? Who or what is its subject and to whom or what does it give voice? Under what conditions is thinking learned and to what effects is it achieved? If these questions generally imbue the thought of Gilles Deleuze from "Nietzsche and Philosophy" (1962) up to "Difference and Repetition" (1968), it is arguably in Proust and Signs (1964) that the questions concerning the essence and conditions of thought are elaborated to the greatest extent and effect. Whereas "Nietzsche and Philosophy" and "Difference and Repetition" have been extensively analysed as systematic works of philosophy in their own right, Deleuze’s early work on Proust has not been adequately recognised for its significance in overturning the classical question “what is thinking?” This study sets out to remedy this oversight. The aim of this study is to explicate in what ways the general problem surrounding the experience of thought finds concrete articulation for Deleuze in Proust’s In "Search of Lost Time" (1913‒1927). For it is Proust who not only destroys the image of thought intrinsic to the tradition of philosophy in an iconoclastic fashion, but dramatises the experience of thought as experimentation beyond the figures of the dogmatist, the moralist, and the conformist in philosophy. Johan Sehlberg is a researcher and lecturer in philosophy at Södertörn University. This is his doctoral dissertation.